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(June 30, 2021)

Only one keyword is necessary in the *$rem* section to activate the response
module. All other options are controlled through the *$response* input section.

RESPONSE

Activate the general response property module.

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

FALSE (or 0)
Don’t activate the general response property module.
TRUE (or 1)
Activate the general response property module.

RECOMMENDATION:

None.

ORDER

Sets the maximum order of response theory to perform.

INPUT SECTION: *$response*

TYPE:

STRING

DEFAULT:

LINEAR

OPTIONS:

LINEAR
Perform up through linear response.

RECOMMENDATION:

None. Currently, only linear response is implemented.

SOLVER

Sets the algorithm for solving the response equations.

INPUT SECTION: *$response*

TYPE:

STRING

DEFAULT:

DIIS

OPTIONS:

LINEAR
Iteratively solve the response equations without convergence acceleration.
DIIS
Iteratively solve the response equations using DIIS for convergence acceleration.

RECOMMENDATION:

DIIS

HAMILTONIAN

Sets the approximation used for the orbital Hessian.

INPUT SECTION: *$response*

TYPE:

STRING

DEFAULT:

RPA

OPTIONS:

RPA
No approximations.
TDA
Same as the CIS approximation.
CIS
Synonym for TDA.

RECOMMENDATION:

None.

SPIN

Does the operator access same spin (singlet) or different spin (triplet) states?

INPUT SECTION: *$response*

TYPE:

STRING

DEFAULT:

SINGLET

OPTIONS:

SINGLET
Operator is spin-conserving.
TRIPLET
Operator is not spin-conserving.

RECOMMENDATION:

None. Care must be taken as *all* operators in a single calculation
will be forced to follow this option.

MAXITER

Maximum number of iterations.

INPUT SECTION: *$response*

TYPE:

INTEGER

DEFAULT:

60

OPTIONS:

$n$
Maximum number of iterations.

RECOMMENDATION:

Use the default value.

CONV

Convergence threshold. For the DIIS solver, this is the DIIS error norm. For
the linear solver, this is the response vector RMSD between iterations.

INPUT SECTION: *$response*

TYPE:

INTEGER

DEFAULT:

8

OPTIONS:

$n$
Sets the convergence threshold to ${10}^{-n}$.

RECOMMENDATION:

Use the default value.

DIIS_START

Iteration number to start DIIS. Before this, linear iterations are performed.

INPUT SECTION: *$response*

TYPE:

INTEGER

DEFAULT:

1

OPTIONS:

$n$
Iteration number to start DIIS.

RECOMMENDATION:

Use the default value.

DIIS_VECTORS

Maximum number of DIIS vectors to keep.

INPUT SECTION: *$response*

TYPE:

INTEGER

DEFAULT:

7

OPTIONS:

$n>0$
Maximum number of DIIS vectors to keep.

RECOMMENDATION:

Use the default value.

RHF_AS_UHF

Should the response equations be solved as though an unrestricted reference is being used?

INPUT SECTION: *$response*

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Treat an RHF wavefunction as though it were UHF.
FALSE
Treat an RHF wavefunction as RHF.

RECOMMENDATION:

Use the default value. Only useful for debugging.

PRINT_LEVEL

Sets a general printing level across the response module.

INPUT SECTION: *$response*

TYPE:

INTEGER

DEFAULT:

2

OPTIONS:

1
Print the initial guess and the final results.
2
1 + iterations and comments.
10
Kill trees.

RECOMMENDATION:

Use the default value.

RUN_TYPE

Should a single response calculation be performed, or should all
permutations of the orbital Hessian and excitation type be performed?

INPUT SECTION: *$response*

TYPE:

STRING

DEFAULT:

SINGLE

OPTIONS:

SINGLE
Use only the orbital Hessian and excitation type specified in
their respective keywords.
ALL
Use all permutations of RPA/TDA and singlet/triplet.

RECOMMENDATION:

Use the default value, unless a comparison between approximations and
excitation types is desired.

SAVE

Save any quantities to disk?

INPUT SECTION: *$response*

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Don’t save any quantities to disk.
1
Save quantities in MO basis.
2
Save quantities in MO and AO bases.

RECOMMENDATION:

None.

READ

Read any quantities from disk?

INPUT SECTION: *$response*

TYPE:

INTEGER

DEFAULT:

0

OPTIONS:

0
Don’t read any quantities from disk.
1
Read quantities in MO basis.
2
Read quantities in AO basis.

RECOMMENDATION:

None.

DUMP_AO_INTEGRALS

Should AO-basis property integrals be saved to disk?

INPUT SECTION: *$response*

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
Save AO-basis property integrals to disk.
FALSE
Don’t save AO-basis property integrals to disk.

RECOMMENDATION:

None.

FORCE_NOT_NONORTHOGONAL

Should the canonical response equations be solved, ignoring the identity of
the underlying orbitals?

INPUT SECTION: *$response*

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
FALSE

RECOMMENDATION:

Leave as false. Using the standard (canonical) response equations with
non-orthogonal MOs will give incorrect results.

FORCE_NONORTHOGONAL

Should the non-orthogonal response equations be solved, ignoring the
identity of the underlying orbitals?

INPUT SECTION: *$response*

TYPE:

LOGICAL

DEFAULT:

FALSE

OPTIONS:

TRUE
FALSE

RECOMMENDATION:

Leave as false. When used with canonical MOs, this should give the same
answer as with the standard equations, but at greater computational cost.

FREQUENCY

Strength of one or more incident fields in atomic units. A separate response
calculation will be performed for every field strength. 0.0 corresponds to
the static limit.

INPUT SECTION: *$response*

TYPE:

DOUBLE

DEFAULT:

0.0

OPTIONS:

$lmn\mathrm{\dots}$
One or more field strengths separated by spaces.

RECOMMENDATION:

None.