List of all sections and keywords¶

selection type: [string]

Keyword to give the type of atom selection. Required keyword.

Valid keyword values are:

• list A list of atoms will be given

• range A range of atoms will be given

• central atom A central atom and a radius will be given

[method string]: [list, range or radius]

Keyword to give the list, range or radius for an active space treated at the given level of theory.

Valid method strings:

• hf

• ccs

• cc2

• ccsd

• cc3

• ccsd(t)

A list is specified using set notation: {1,2,3}.

A range is specified as [1,3] (equivalent to {1,2,3}).

A radius is specified by a double precision real (e.g. 1.0d2) and is always in Angstrom units. The atoms within the radius \(r\) of the central atom then define the active atoms.

Example: First three atoms in the input are chosen as HF active atoms space.

active atoms
   selection type: list
   hf: {1,2,3}
end active atoms

central atom: [integer]

Specifies the central atom in the active space. Requested for selection type: central atom.

inactive basis: [string]

Specifies the basis set on the inactive atoms, that is the atoms not specified in the active atoms section. Optional.

Valid keyword values are basis sets available in \(e^T\).

[method string] basis: [string]

Set basis for active space treated at a given level of theory. Optional.

Valid method strings:

• hf

• ccs

• cc2

• ccsd

• cc3

• ccsd(t)

Valid keyword values are basis sets available in \(e^T\).

Example: First three atoms in the input are chosen as CCSD active atoms space with aug-cc-pVDZ basis.

active atoms
   selection type: range
   ccsd: [1,3]
   ccsd basis: aug-cc-pVDZ
end active atoms

Bath orbital

Default: false

Add a bath orbital to the calculation with zero orbital energy and zero electron repulsion integrals.

dipole

Calculation of coupled cluster ground state dipole moment.

quadrupole

Calculation of coupled cluster ground state quadrupole moment.

polarizabilities

Enables the calculation of polarizabilities.

transition moments

Enables the calculation of transition moments.

eom

Properties will be calculated within the equation of motion formalism.

Either this or the lr keyword must be specified.

Available for CCS, CC2, CCSD, and CC3.

lr

Properties will be calculated within the linear response formalism.

Either this or the eom keyword must be specified.

Available for CCS, CC2, and CCSD.

dipole length

Required keyword. Currently the only operator available for response calculations in \(e^T\).

frequencies: {[real], [real], ...}

Frequencies, in Hartree, for which the polarizability shall be computed. Required for polarizabilities.

initial states: {[real], [real], ...}

Default: {0} (Only the ground state is considered.)

Numbers of the states for which the transition/permanent moments shall be computed.

permanent moments

Enables the calculation of permanent moments.

propagation

Default: false

Perform real-time propagation of the coupled-cluster state.

fft dipole moment

Default: false

Perform complex fast Fourier transform of the dipole moment time series from an earlier real-time propagation calculation.

fft electric field

Default: false

Perform complex fast Fourier transform of the electric field time series from an earlier real-time propagation calculation.

cholesky eri

Keyword to run a Cholesky decomposition of the two-electron integrals. Note that this is done automatically for any coupled cluster calculation, the keyword should only be given if only Cholesky decomposition is to be performed.

ground state

Keyword to run a ground state calculation at the level of theory given in the method section. Enables the ground state or reference engine.

ground state geoopt

Keyword to run a Hartree-Fock ground state geometry optimization. Enables the ground state geometry optimization engine.

mean value

Keyword to calculate coupled cluster expectation values. Enables the mean value engine, which determines the coupled cluster ground state amplitudes and multipliers, and calculates the requested expectation value. Which mean value(s) to calculate are specified in the cc mean value section.

excited state

Keyword to run a coupled cluster excited state calculation. Enables the excited state engine, which calculates the ground and excited state amplitudes.

response

Keyword to enable the coupled cluster response engine. Implemented features are EOM transition moments and polarizabilities for CCS, CC2, CCSD and CC3, and LR transition moments and polarizabilities for CCS. The response engine drives the calculation of ground state amplitudes and multipliers, excited state vectors (left and right eigenvectors of the Jacobian matrix) and the requested property.

restart

Global restart keyword to activate restart where possible.

time dependent state

Keyword to run coupled cluster time propagation. Enables the time-dependent engine.

tdhf excited state

Keyword to run TDHF excitation energies (Tamm-Dancoff or RPA).

tdhf response

Keyword to run TDHF response calculation (polarizabilities).

envelope: {[integer],[integer],...}

Specifies the envelopes to use for electric field pulse \(1,2,\ldots\).

Valid keyword values are:

• 1 Use Gaussian envelope.

• 2 Use sine squared envelope.

x polarization: {[real], [real], ...}

\(x\) polarization for electric field pulse \(1,2,\ldots\).

y polarization: {[real], [real], ...}

\(y\) polarization for electric field pulse \(1,2,\ldots\).

z polarization: {[real], [real], ...}

\(z\) polarization for electric field pulse \(1,2,\ldots\).

central time: {[real], [real], ...}

Specifies the central time of electric field pulse \(1,2,\ldots\).

width: {[real], [real], ...}

Specifies the temporal widths of electric field pulse \(1,2,\ldots\) in atomic units. The width corresponds to the Gaussian root-mean-squared width of a pulse with a Gaussian envelope and the period of a pulse with a sine squared envelope.

central angular frequency: {[real], [real], ...}

Specifies the central angular frequencies of electric field pulse \(1,2,\ldots\) in atomic units.

peak strength: {[real], [real], ...}

Specifies the amplitude of the carrier wave of electric field pulse \(1,2,\ldots\) in atomic units.

phase shift: {[real], [real], ...}

Specifies the (carrier-envelope) phase shifts of electric field pulse \(1,2,\ldots\). The shift corresponds to the difference between the middle of the envelope and the maximum of the carrier wave.

repetition: {[real], [real], ...}

Default: {1,1,...} (a single instance of each pulse)

Number of instances of electric field pulse \(1,2,\ldots\). The separation of the repeated pulses can be specified by the separation keyword.

separation: {[real], [real], ...}

Number of repetitions (copies) of electric field pulse \(1,2,\ldots\).

dipole

Calculation of the FCI ground state dipole moment.

quadrupole

Calculation of the FCI ground state quadrupole moment.

hf

Default: false

This enables the freezing of Hartree-Fock orbitals after they are converged. Optional.

core

Default: false

This enables the frozen core approximation. Optional.

dipole

Calculation of the HF dipole moment.

quadrupole

Calculation of the HF quadrupole moment.

cholesky storage: [string]

Default: memory if they take up less than 20% of the total memory; disk otherwise

Specify how to store the Cholesky vectors. Optional.

Valid options are:

• memory Store Cholesky vectors in memory.

• disk Store Cholesky vectors on file.

eri storage: [string]

Default: memory if the entire matrix is needed in the calculation and they take up less than 20% of the total memory; none otherwise

Specify how to store the electron repulsion integrals. Optional.

Valid options are:

• memory Store full electron repulsion matrix in memory.

• none Always construct the integrals from Cholesky vectors.

mo eri in memory

Default: false

Override defaults and store full MO ERI matrix in memory if true. Recommended for time-dependent CC.

t1 eri in memory

Default: false

Override defaults and store full T1 ERI matrix in memory if true.

ri: [string]

Default: None

Enables the RI approximation for the integrals and provides the auxiliary basis set.

Valid options are any available auxiliary basis set.

available: [integer]

Default: 8

Specifies the available memory, default units are gigabytes. Optional.

unit: [string]

Default: GB

Specifies the units for the specified available memory. Optional.

Valid keyword values are:

• B

• KB

• MB

• GB

levels: [string], [string], ...

Specifies the level of theory for the different active spaces. Required keyword.

Valid keyword values are:

• ccs

• cc2

• ccsd

cc2 orbitals: [string]

Specifies the type of orbitals used for orbital partitioning in MLCC2. Required keyword.

Valid keyword values are:

• cnto-approx Approximated correlated natural transition orbitals

• cholesky Cholesky orbitals (occupied and virtual)

• cholesky-pao Cholesky occupied orbitals and projected atomic orbitals for the virtuals.

• nto-canonical Natural transition orbitals for occupied and canonical for virtuals.

ccsd orbitals: [string]

Specifies the type of orbitals used for orbital partitioning in MLCCSD. Required keyword.

Valid keyword values are:

• cnto-approx Approximated correlated natural transition orbitals

• cholesky Cholesky orbitals (occupied and virtual)

• cholesky-pao Cholesky occupied orbitals and projected atomic orbitals for the virtuals.

• nto-canonical Natural transition orbitals for occupied and canonical for virtuals.

cholesky threshold: [real]

Default: \(1.0\cdot 10^{-2}\) (or 1.0d-2)

Threshold for the Cholesky decomposition of the density. Only used with cc2 orbitals: cholesky or cc2 orbitals: cholesky-pao

cnto occupied cc2: [integer]

Determines the number of occupied orbitals in the CC2 orbital space for the MLCC2 calculation.

cnto virtual cc2: [integer]

Default: \(n_v^{\text{CC2}} = n_o^{\text{CC2}}\cdot\frac{n_v}{n_o}\)

Sets the number of virtual orbitals in the CC2 orbital space for the MLCC2 calculation. Optional.

cnto occupied ccsd: [integer]

Determines the number of occupied orbitals in the CCSD orbital space for the MLCCSD calculation.

cnto virtual ccsd: [integer]

Default: \(n_v^{\text{CCSD}} = n_o^{\text{CCSD}}\cdot\frac{n_v}{n_o}\)

Sets the number of virtual orbitals in the CCSD orbital space for the MLCCSD calculation. Optional.

cnto states: {[integer], [integer], ...}

Determines which CCS excited states are used to construct the approximated CNTOs.

print ccs calculation

Default: false

Enables the printing of the CCS calculation in the case of cc2 orbitals: cnto-approx or ccsd orbitals: cnto-approx. Optional.

print cc2 calculation

Default: false

Enables the printing of the CC2 calculation in the case of ccsd orbitals: cnto. Optional.

nto occupied cc2: [integer]

Determines the number of occupied orbitals in the CC2 orbital space for the MLCC2 calculation.

nto occupied ccsd: [integer]

Determines the number of occupied orbitals in the CCSD orbital space for the MLCCSD calculation.

nto virtual cc2: [integer]

Determines the number of virtual orbitals in the CC2 orbital space for the MLCC2 calculation. Optional.

canonical virtual cc2: [integer]

Default: \(n_v^{\text{CC2}} = n_o^{\text{CC2}}\cdot\frac{n_v}{n_o}\)

Sets the number of virtual orbitals in the CC2 orbital space for the MLCC2 calculation. Optional.

canonical virtual ccsd: [integer]

Default: \(n_v^{\text{CCSD}} = n_o^{\text{CCSD}}\cdot\frac{n_v}{n_o}\)

Sets the number of virtual orbitals in the CCSD orbital space for the MLCCSD calculation. Optional.

nto states: {[integer], [integer], ...}

Determines which CCS excited states are used to construct the NTOs.

cnto restart

Default: false

If specified, the solver will attempt to restart from previously determined CNTO matrices (M and N). Optional.

orbital restart

Default: false

If specified, orbital partitioning is skipped and MLCC orbitals (and sizes of orbital sets) are read from file. Optional.

forcefield: [string]

Default: non-polarizable

Specifies the forcefield to be used for the MM portion.

Valid keyword values are:

• non-polarizable Electrostatic QM/MM Embedding

  Note

  The charge has to be provided for each atom in the geometry section.

• fq Fluctuating Charge force field.

  Note

  The electronegativity and chemical hardness has to be provided for each atom in the geometry section.

algorithm: [string]

Default: mat_inversion

Selects the algorithm to be used to solve the FQ equation. So far only the inversion algorithm is implemented. Optional.

initial hf optimization

Default: false

Enables an initial optimization of the full density through a standard HF calculation to a low threshold.

initial hf threshold: [real]

Default: \(1.0\cdot10^{-1}\) (or 1.0d-1)

Threshold for the initial HF optimization. Should only be specified if initial hf optimization is also specified.

print initial hf

Default: false

Enables the printing of the initial HF optimization in the case that initial hf optimization is given. Optional.

cholesky virtuals

Default: false

Enable the use of Cholesky decomposition of the virtual AO density to construct the active virtual orbitals. The default is to use projected atomic orbitals.

cholesky threshold: [real]

Default: \(1.0\cdot10^{-2}\) or (1.0d-2)

Threshold for the Cholesky decomposition of the AO density to construct an active space.

project on minimal basis

Default: false

First diagonalization of the AO fock matrix will be performed in a minimal basis.

input: [string]

Specifies if the input parameters are given in the \(e^{T}\) input file or in an external file handled directly by the external library PCMSolver. Required.

Valid keyword values are

• external

  Note

  No further input has to be given to pcm because the parameters have to be specified in an external .pcm-file.

• internal

solvent: [string]

Specifies the solvent outside the cavity.

Valid keyword values

tesserae area: [real]

Default: 0.3

Area of the finite elements (tesserae) the surface is constructed from given in square Angstrom.

solver type: [string]

Default: iefpcm

Selects the type of solver to be used to solve the PCM equation.

Valid keyword values are

• iefpcm Integral Equation Formalism PCM

• cpcm conductor-like PCM

output print level: [string]

Specifies the print level for the main output file. Default is normal. Optional.

Valid keyword values are:

• minimal Only banners, final results like total energies or excitation energies, solver settings, and other essential information.

• normal In addition to minimal, print iteration information, amplitude analysis, and other non-essential information.

• verbose In addition to normal, print all relevant information for users. This can make the output difficult to read and navigate.

• debug In addition to verbose, prints information mostly relevant for debugging code that behaves unexpectedly.

timing print level: [string]

Specifies the print level for the timing file. Default is normal. Optional.

Valid keyword values are:

• minimal Total solver timings, total program time, and other essential timings.

• normal In addition to minimal, iteration times and details like time to calculate omega, the Fock matrix, and other expensive terms.

• verbose In addition to normal, times for subtasks, such as micro-iteration times as well as individual contributions to the omega vector.

• debug In addition to verbose, prints timings mostly relevant for debugging code that behaves unexpectedly.

full references

If specified, implementation references will be printed in APA style. Otherwise, only the DOIs are printed to the output file.

z-matrix

If specified, prints the z-matrix to the output file.

coupling: {[real], ...}

Default: 0.0

Specifies the light-matter coupling \(\lambda= \sqrt{4\pi/V_{\text{eff}}}\) in atomic units.

frequency: {[real], ...}

Specifies the photon frequency/energy (\(\omega\)) in atomic units.

modes: [integer]

Specifies the number of photon modes in the QED calculation.

polarization: {[real],[real],[real]}

Specifies the transversal polarization vector (\(\vec{\epsilon}\)).

wavevector: {[real],[real],[real]}

Specifies the direction of the wavevector (\(\vec{k}\)).

coupling bilinear: {[real], ...}

Overwrites the bilinear light-matter coupling \(\lambda \sqrt{\omega/2}\).

coupling self: {[real], ...}

Overwrites the light-matter self-coupling \(0.5 \lambda^2\).

coherent state: {[real], ...}

Specifies the coherent state for each photon mode.

hf coherent state: {[real], ...}

Specifies the coherent state for each photon mode. Only used in QEDHF.

quadrupole oei

Assume complete basis (\(\sum_p |p\rangle\langle p| = 1\)) to rewrite the self-interaction with quadrupole moments, removing references to the virtual density.

singlet states: [integer]

Specifies the number of singlet excited states to calculate.

triplet states: [integer]

Specifies the number of triplet excited states to calculate.

algorithm: [string]

Default: davidson for CCS, CC2, MLCC2, and CCSD; non-linear davidson for lowmem-CC2 and CC3.

Solver to use for converging the excited state equations.

Valid keyword values are:

• davidson

  Use Davidson algorithm with residuals preconditioned with the orbital differences approximation of the Jacobian. Cannot be used for lowmem-CC2 and CC3.

• diis

  Use DIIS algorithm with update estimates obtained from the orbital differences approximation of the Jacobian. Can be used for lowmem-CC2 and CC3.

• non-linear davidson

  Use the non-linear Davidson algorithm with residuals preconditioned with the orbital differences approximation of the Jacobian. Can be used for lowmem-CC2 and CC3.

• asymmetric lanczos

  Use the asymmetric Lanczos algorithm for excitation energies. EOM oscillator strengths will be calculated as well. Cannot be used for lowmem-CC2, MLCC2, and CC3.

chain length: [integer]

Specifies the dimension of the reduced (Krylov sub-) space for the asymmetric Lanczos algorithm. Required for algorithm: asymmetric lanczos.

right eigenvectors

Default: true

If specified, solve for the right eigenvectors of the Jacobian matrix. This keyword should only be specified for an excited state calculation. For property calculations, the program will solve for both left and right vectors. Optional.

left eigenvectors

Default: false

If specified, solve for the left eigenvectors of the Jacobian matrix. This keyword should only be specified for an excited state calculation. For property calculations, the program will solve for both left and right vectors. Optional.

energy threshold: [real]

Default: \(10^{-3}\) (or 1.0d-3)

Energy convergence threshold, as measured with respect to the previous iteration. Optional.

residual threshold: [real]

Default: \(10^{-3}\) (or 1.0d-3)

Threshold of the \(L^{2}\)-norm of the residual vector of the excited state equation. Optional

core excitation: { integer, integer, ... }

Default: false

Solve for core excitations within the CVS approximation. The integers specify which orbitals to excite out of. Orbitals are ordered according to orbital energy (canonical orbitals). If the keyword has been specified, CVS will be activated automatically. Optional.

remove core: { integer, integer, ... }

Default: false

Valence excitations, but with excitations from core MOs projected out. The integers specify which core orbitals from which one should not excite. Orbitals are ordered according to orbital energy (canonical orbitals). Optional.

ionization

Default: false

Solve for ionized state. If this keyword is specified, the ionized state will be calculated using a bath orbital and projection similar to CVS. Optional.

max iterations: [integer]

Default: 100

The maximum number of iterations. The solver stops if the number of iterations exceeds this number. Optional.

diis dimension: [integer]

Default: 20

Number of previous DIIS records to keep. Optional.

restart

Default: false

If specified, the solver will attempt to restart from a previous calculation. Optional.

storage: [string]

Default: disk

Selects storage of excited state records. Optional.

Valid keyword values are:

• memory Stores records in memory.

• disk Stores records on file.

crop

Default: false

If specified, the CROP version of DIIS will be enabled. Optional.

max reduced dimension: [integer]

Default: \(\max(100, 10 n_\mathrm{s})\), where \(n_\mathrm{s}\) is the number of singlet states specified by singlet states: [integer] in the solver cc es section.

The maximal dimension of the reduced space of the Davidson procedure. Optional.

lanczos normalization: [integer]

Default: asymmetric

Specifies the type of biorthonormalization for the asymmetric Lanczos algorithm. Optional.

Valid keyword values are:

• asymmetric Which enables \(\tilde{p} = p\) and \(\tilde{q} = \frac{q}{p\cdot q}\)

• symmetric Which enables \(\tilde{p} = \frac{p}{\sqrt{|p\cdot q|}}\) and \(\tilde{q} = \text{sgn}(p\cdot q)\frac{q}{\sqrt{|p\cdot q|}}\)

max micro iterations: [integer]

Default: \(100\)

Maximum number of iterations in the non-linear Davidson solver. Optional.

rel micro threshold: [real]

Default: \(10^{-1}\) (or 1.0d-1)

Threshold for convergence in the micro iterations of the non-linear Davidson solver. This threshold is relative to the current norm of the residuals.

state guesses: {i=integer, a=integer}, {i=integer, a=integer}

Specifies start guesses for excited states in terms of transitions from occupied orbital \(i\) to virtual \(a\). Optional.

algorithm: [string]

Default: newton-raphson for CC3, diis for other coupled cluster methods

Solver to use for converging the amplitude equations. Optional.

Valid keyword values are:

• diis Quasi-Newton algorithm accelerated by DIIS. Uses the orbital differences approximation of the coupled cluster Jacobian.

• newton-raphson. Newton algorithm accelerated by DIIS.

energy threshold: [real]

Default: \(10^{-5}\) (or 1.0d-5)

Energy convergence threshold, as measured with respect to the previous iteration. Optional.

omega threshold: [real]

Default: \(10^{-5}\) (or 1.0d-5)

Threshold of the \(L^{2}\)-norm of the amplitude equations vector \(\Omega_\mu = \langle \mu \vert \bar{H} \vert \text{HF} \rangle\). Optional.

multimodel newton: [string]

Default: on for CC3, off for other coupled cluster methods

If specified as on, the Newton-Raphson algorithm will solve the micro-iterations using a lower-level approximation of the Jacobian matrix. Must be combined with algorithm: newton-raphson. Optional.

crop

Default: false

If specified, the CROP version of DIIS will be enabled. Optional.

max iterations: [integer]

Default: 100

The maximum number of iterations. The solver stops if the number of iterations exceeds this number. Optional.

max micro iterations: [integer]

Default: 100

The maximum number of micro-iterations in the exact Newton solver (see algorithm: newton-raphson). The solver stops if the number of iterations exceeds this number. Optional.

rel micro iterations: [real]

Default: \(10^{-2}\) (or 1.0d-2)

The relative threshold \(\tau\) used for micro-iterations by the exact Newton solver (see algorithm: newton-raphson). The micro-iterations are considered converged if the \(L^{2}\)-norm of the Newton equation is less than \(\tau \vert\vert \boldsymbol{\Omega} \vert\vert\). Optional.

storage: [string]

Default: disk

Selects storage of DIIS records in coupled cluster calculations. Optional.

Valid keyword values are:

• memory Stores DIIS records in memory.

• disk Stores DIIS records on file.

micro iteration storage: [string]

Default: value of the keyword storage

Selects storage of records in the micro iterations (if any) in ground state coupled cluster calculations. Optional.

Valid keyword values are:

• memory Stores records in memory.

• disk Stores records on file.

diis dimension: [integer]

Default: 8

Number of previous DIIS records to keep. Optional.

restart

Default: false

If specified, the solver will attempt to restart from a previous calculation. Optional.

algorithm: [string]

Default: diis for ccs, lowmem-cc2, cc2, and cc3; davidson for other coupled cluster models.

Solver to use for converging the multiplier equation. Not supported for MLCC2.

Valid keyword values are:

• davidson Use Davidson algorithm with residuals preconditioned with orbital differences approximation of the Jacobian. Cannot currently be used for lowmem-CC2, CC2, and CC3.

• diis Use DIIS algorithm with update estimates obtained from the orbital differences approximation of the Jacobian. Must be used for lowmem-CC2, CC2, and CC3.

threshold: [real]

Default: \(10^{-5}\) (or 1.0d-5)

Threshold of the \(L^{2}\)-norm of the residual vector of the multiplier equation. Optional.

max iterations: [integer]

Default: 100

The maximum number of iterations. The solver stops if the number of iterations exceeds this number. Optional.

diis dimension: [integer]

Default: 20

Number of previous DIIS records to keep. Optional.

restart

Default: false

If specified, the solver will attempt to restart from a previous calculation. Optional.

storage: [string]

Default: disk

Selects storage of solver subspace records. Optional.

Valid keyword values are:

• memory Stores records in memory.

• disk Stores records on file.

crop

Default: false

If specified, the CROP version of DIIS will be enabled. Optional.

max reduced dimension: [integer]

Default: 100

The maximal dimension of the reduced space of the Davidson procedure. Optional.

integrator: [string]

Specifies the integration method used for real-time propagation. Required.

Valid keyword values are:

• rk4 Fourth-order Runge-Kutta (RK4)

• gl2 Second-order Gauss-Legendre (GL2)

• gl4 Fourth-order Gauss-Legendre (GL4)

• gl6 Sixth-order Gauss-Legendre (GL6)

initial time: [real]

The start time for the real-time propagation given in atomic units. Required.

final time: [real]

The end time for the real-time propagation given in atomic units. Required.

time step: [real]

Size of the time steps for the real-time propagation given in atomic units. Required.

steps between output: [integer]

Default: \(1\)

Specifies how many time steps the solver should take between each time output (energy, dipole moment, …) is written to file. Optional.

implicit treshold: [real]

Default: \(10^{-11}\) (or 1.0d-11)

Specifies how tightly the Euclidian norm of the residual of implicit Runge-Kutta methods should converge before going to the next time step. Optional.

energy output

Default: false

Write energy to file every steps between output. Optional.

dipole moment output

Default: false

Write dipole moment to file every steps between output. Optional.

electric field output

Default: false

Write electric field to file every steps between output. Optional.

amplitudes output

Default: false

Write cluster amplitudes to file every steps between output. Optional.

multipliers output

Default: false

Write multipliers to file every steps between output. Optional.

density matrix output

Default: false

Write molecular orbital (MO) density matrix to file every steps between output. Optional.

threshold: [real]

Default: \(10^{-3}\) (or 1.0d-3)

Residual norm threshold for convergence. Optional.

storage: [string]

Default: disk

Storage for Davidson records. Optional.

Valid options are:

• disk Store records on file.

• memory Store records in memory.

max iterations: [real]

Default: \(100\)

The maximum number of iterations. The solver stops if the number of iterations exceeds this number. Optional.

threshold: [real]

Default: \(10^{-4}\) (or 1.0d-4).

Decomposition threshold. All electron repulsion integrals will be reproduced by the Cholesky vectors to within this threshold. This threshold puts an upper limit to the accuracy of coupled cluster calculations. Optional.

batches: [integer]

Default: 1

Number of batches \(n_b\) in partitioned Cholesky decomposition. In this procedure, the Cholesky basis is chosen from a reduced set generated by decomposing diagonal blocks of the matrix (of which there are \(n_b\)). Introduces an error of about an order of magnitude higher than threshold. Optional.

one center

Default: false

If specified, the Cholesky decomposition is restricted to diagonal elements \(g_{\alpha\beta,\alpha\beta}\) for which both atomic orbital indices, \(\alpha\) and \(\beta\) , are centered on the same atom. Introduces an error of about \(10^{-3}\) that cannot be reduced further by threshold. Optional.

span: [real]

Default: \(10^{-2}\) (or 1.0d-2)

Span factor \(\sigma\) . For a given iteration of the Cholesky decomposition, this number determines the range of possible pivots to select/qualify: \(D_{\alpha\beta} \geq \sigma D_\mathrm{max}\) . Optional.

qualified: [integer]

Default: \(1000\)

Maximum number of qualified pivots in an iteration of the Cholesky decomposition. Optional.

mo screening

Perform Cholesky decomposition such that the MO electron repulsion integrals are targeted. The default screening targets the AO integrals.

energy threshold: [real]

Default: \(10^{-6}\) (or 1.0d-6)

Energy convergence threshold, as measured with respect to the previous iteration. Optional.

residual threshold: [real]

Default: \(10^{-6}\) (or 1.0d-6)

Threshold of the \(L^{2}\)-norm of the residual vector of the FCI equation. Optional

max reduced dimension: [integer]

Default: 100

The maximal dimension of the reduced space of the Davidson procedure. Optional.

max iterations: [integer]

Default: 100

The maximum number of iterations. The solver stops if the number of iterations exceeds this number. Optional.

start guess: [string]

Default: single determinant

Specifies start guesses for FCI. Optional.

Valid keyword values are:

• single determinant Set a single element of the FCI vector to one for every state. For the ground state it corresponds to the HF determinant.

• random Gives random starting guess to the coefficient of the FCI vector.

states: [integer]

Default: 1

Specifies the number of states to calculate. Optional.

restart

Default: false

If specified, the solver will attempt to restart from a previous calculation. Optional.

storage: [string]

Default: disk

Selects storage of records for the CI vectors. Optional.

Valid keyword values are:

• memory Stores records in memory.

• disk Stores records on file.

initial time: [real]

Specifies the start of the interval of interest in the time series file to Fourier transform. Required.

final time: [real]

Specifies the end of the interval of interest in the time series file to Fourier transform. Required.

time step: [real]

Specifies the time step between the data points in the time series file to Fourier transform. Required.

algorithm: [string]

Default: scf-diis

Selects the solver to use.

Valid keyword values are:

• scf-diis AO-based self-consistent Roothan-Hall algorithm with direct inversion of the iterative subspace (DIIS) acceleration.

• scf Self-consistent Roothan-Hall algorithm.

• mo-scf-diis MO-based self-consistent Roothan-Hall algorithm with DIIS acceleration. Recommended for multilevel Hartree-Fock (MLHF).

• level-shift-newton-raphson MO-based second-order trust-region step-constrained optimization procedure.

energy threshold: [real]

Default: \(10^{-7}\) (or 1.0d-7)

Energy convergence threshold, as measured with respect to the previous iteration.

gradient threshold: [real]

Default: \(10^{-7}\) (or 1.0d-7)

Gradient threshold \(\tau\). The equations have converged if \(\max \mathbf{G} < \tau\).

storage: [string]

Default: memory

Selects storage of DIIS records.

Valid keyword values are:

• memory Stores DIIS records in memory.

• disk Stores DIIS records on file.

print orbitals

Default: false

If specified, the *mo_coefficients.out file is created and copied to the working directory by eT_launch.

write molden

Default: false

If specified, a molden input file called *.molden is created and copied to the working directory by eT_launch.

crop

Default: false

If specified, the conjugate residual with optimal trial vectors (CROP) version of DIIS will be enabled.

cumulative fock threshold: [real]

Default: \(1.0\) (or 1.0d0)

When the gradient max-norm reaches this threshold, the Fock matrix is built using the difference in the density matrix relative to the previous iteration. When the max-norm exceeds the threshold, the Fock matrix is built directly using the current density matrix.

max iterations: [integer]

Default: \(100\)

The maximum number of iterations. The solver stops if the number of iterations exceeds this number.

diis dimension: [integer]

Default: \(8\)

Number of previous DIIS records to keep.

restart

Default: false

If specified, the solver will attempt to restart from a previous calculation.

skip

Default: false

If specified, orbitals will be read from file, the convergence of the gradient will be checked, but the rest of the SCF solver will be skipped.

ao density guess: [string]

Default: sad

Which atomic orbital density matrix to use as start guess.

Valid keyword values are:

• sad Use the superposition of atomic densities (SAD) guess. This is built on-the-fly by performing spherically averaged UHF calculations on each unique atom (and basis) in the specified molecular system.

• core Use the density obtained by approximating the Fock matrix by its one-electron contribution and performing one Fock diagonalization.

coulomb threshold: [real]

Default: \(10^{-6}*(\text{gradient threshold})\)

The threshold for neglecting Coulomb contributions to the two-electron part of the AO Fock matrix.

Default: \(\text{(coulomb threshold)}^2\)

The \(\epsilon\) value for Libint 2. Gives the precision in the electron repulsion integrals.

integral cutoff: [real]

Default: \(\text{(coulomb threshold)}\)

Shell-pairs for which all the electron repulsion integrals are smaller than this value are neglected in the Fock matrix construction.

one-electron integral cutoff: [real]

Default: \(\text{(coulomb threshold)}\cdot10^{-5}\)

One-electron Hamiltonian integrals are neglected for a shell-pair for which all the overlap integrals are smaller than this value.

coulomb exchange terms: [string]

Default: collective

Determines if the two-electron part of the Fock matrix (G(D)) is computed at once or if Coulomb and exchange contributions are calculated separately.

Valid keyword values are:

• collective

• separated

rohf coupling parameters: [string]

Default: guest-saunders

Coupling parameters \(\vec{A}, \vec{B}\) for the ROHF orbitals, see for instance J. Chem. Phys. 125, 204110 (2006).

Valid keyword values are:

• guest-saunders : \(\vec{A} = (1/2, 1/2, 1/2), \vec{B}=(1/2, 1/2, 1/2)\)

• mcweeny-diercksen: \(\vec{A} = (1/3, 1/3, 2/3), \vec{B}=(2/3, 1/3, 1/3)\)

• faegri-manne: \(\vec{A} = (1/2, 1, 1/2), \vec{B}=(1/2, 0, 1/2)\)

algorithm: [string]

Default: bfgs

Selects the solver to use. Optional.

Valid keyword values are:

• bfgs A Broyden-Fletcher-Goldberg-Shanno (BFGS) solver using redundant internal coordinates and a rational function (RF) level shift obtained from an augmented Hessian.

max step: [real]

Default: \(0.5\) (or 0.5d0)

Maximum accepted step length in \(L^{2}\)-norm. Rescales the step to the boundary otherwise. Optional.

energy threshold: [real]

Default: \(10^{-4}\) (or 1.0d-4)

Energy convergence threshold, as measured with respect to the previous iteration. Optional.

gradient threshold: [real]

Default: \(10^{-4}\) (or 1.0d-4)

Threshold of the \(L^{2}\)-norm of the energy gradient. Optional.

max iterations: [integer]

Default: 100

The maximum number of iterations. The solver stops if the number of iterations exceeds this number. Optional.

restart

Default: false

If specified, the solver will attempt to restart from a previous calculation. Optional.

forward difference

Default: false

If specified, the solver uses numerical gradients of type forward difference

central difference

Default: false

If specified, the solver uses numerical gradients of type central difference

singlet states: [integer]

Specifies the number of singlet excited states to calculate.

energy threshold: [real]

Default: \(10^{-3}\) (or 1.0d-3)

Energy convergence threshold, as measured with respect to the previous iteration. Optional.

max iterations: [integer]

Default: 100

The maximum number of iterations. The solver stops if the number of iterations exceeds this number. Optional.

max reduced dimension: [integer]

Default: 50

The maximal dimension of the reduced space of the Davidson procedure. Optional.

residual threshold: [real]

Default: \(10^{-3}\) (or 1.0d-3)

Threshold of the \(L^{2}\)-norm of the residual vector of the excited state equation. Optional.

restart

Default: false

If specified, the solver will attempt to restart from a previous calculation. Optional.

storage: [string]

Default: memory

Selects storage of excited state records. Optional.

Valid keyword values are:

• memory Stores records in memory.

• disk Stores records on file.

tamm-dancoff

Default: false

Enables the Tamm-Dancoff approximation. Optional.

max iterations: [integer]

Default: 100

The maximum number of iterations. The solver stops if the number of iterations exceeds this number. Optional.

max reduced dimension: [integer]

Default: 100

The maximal dimension of the reduced space of the Davidson procedure. Optional.

residual threshold: [real]

Default: \(10^{-3}\) (or 1.0d-3)

Threshold of the \(L^{2}\)-norm of the residual vector of the response equation. Optional.

frequencies: [list of reals]

Default: None

Frequencies for frequency-dependent polarizabilities. Static polarizabilities are obtained either by specifying frequency zero, or by not giving this keyword. Optional.

print iterations

Default: false

Enables the printing of the iterations of the response solver. Optional.

singlet states: [integer]

Specifies the number of singlet excited states to calculate.

energy threshold: [real]

Default: \(10^{-3}\) (or 1.0d-3)

Energy convergence threshold, as measured with respect to the previous iteration. Optional.

max iterations: [integer]

Default: 100

The maximum number of iterations. The solver stops if the number of iterations exceeds this number. Optional.

max reduced dimension: [integer]

Default: 50

The maximal dimension of the reduced space of the Davidson procedure. Optional.

residual threshold: [real]

Default: \(10^{-3}\) (or 1.0d-3)

Threshold of the \(L^{2}\)-norm of the residual vector of the excited state equation. Optional.

restart

Default: false

If specified, the solver will attempt to restart from a previous calculation. Optional.

storage: [string]

Default: memory

Selects storage of excited state records. Optional.

Valid keyword values are:

• memory Stores records in memory.

• disk Stores records on file.

tamm-dancoff

Default: false

Enables the Tamm-Dancoff approximation. Optional.

name: [string]

Default: none

Specifies the name of the calculation, which is printed in the output file.

charge: [integer]

Default: \(0\)

Specifies the charge of the system.

multiplicity: [integer]

Default: \(1\)

Specifies the spin multiplicity of the system.

cartesian gaussians

Enforce cartesian Gaussians basis functions for all atoms. Default for Pople basis sets.

pure gaussians

Enforce spherical Gaussian basis functions for all atoms. Default for all basis sets except Pople basis sets.

print orbitals

Print orbital coefficients to *mo_information.out files when the orbital coefficients change, e.g. when frozen hf or MLCC are used.

file format: [string]

Default: plt

Specify format of the output files containing the grid data. Optional.

Valid options are:

• plt

• cube

grid buffer: [real]

Default: \(2.0\) (or 2.0d0)

Sets the distance between the edge of the grid (x, y, and z direction) and the molecule in Angstrom units. Optional.

grid max: {[real], [real], [real]}

Sets the maximum values of the grid in x, y and z direction in Angstrom. Optional.

grid min: {[real], [real], [real]}

Sets the minimum values of the grid in x, y and z direction in Angstrom. Optional.

grid spacing: [real]

Default: \(0.1\) (or 1.0d-1)

Sets the spacing between grid points for the visualization given in Angstrom units. Optional.

plot cc density

Plots the coupled cluster density. Optional.

plot es densities

Plots the coupled cluster excited state densities for the states to plot. Optional.

plot hf active density

Plots the active HF density in the case of a reduced space calculation. Optional.

plot hf density

Plots the HF density. Optional.

plot hf orbitals: {[integer], [integer], ...}

Plots the canonical orbitals given in the comma separated list. Optional.

plot transition densities

Plots the coupled cluster transition densities for the states to plot. Optional.

states to plot: {[integer], [integer], ...}

List of integers specifying which densities should be plotted.

plot cc orbitals: {[integer], [integer], ...}

Plots the orbitals given in the comma separated list from a CC wave function. Optional.