RESPONSE_SOLVER

Description: Specify how atomic blocks should be clustered in the used matrices, in order to improve flop rate, and possibly speedup the matrix multiply. Note that the atomic s_preconditioner can not be used. Furthermore, since screening is on matrix blocks, slightly more accurate results can be expected with molecular. [Edit on GitHub]

Valid values:

ATOMIC Using atomic blocks
MOLECULAR Using molecular blocks.

MAX_ITER

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Type: integer
Default: 50
Usage: MAX_ITER 200

Description: Maximum number of conjugate gradient iteration to be performed for one optimization. [Edit on GitHub]

MAX_ITER_LANCZOS

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Type: integer
Default: 128
Usage: MAX_ITER_LANCZOS 128

Description: Maximum number of lanczos iterations. [Edit on GitHub]

METHOD

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Type: enum
Default: AO_ORTHO
Usage: METHOD SOLVER

Description: Algorithm used to solve response equation. Both solver are conjugate gradient based, but use either a vector (MO-coefficient) or density matrix formalism in the orthonormal AO-basis to obtain response density [Edit on GitHub]

Valid values:

MO_SOLVER Solver based on MO (vector) formalism
AO_ORTHO Solver based on density matrix formalism

PRECONDITIONER

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Type: enum
Default: MULTI_LEVEL
Usage: PRECONDITIONER FULL_ALL

Description: Type of preconditioner to be used with MO conjugate gradient solver. They differ in effectiveness, cost of construction, cost of application. Properly preconditioned minimization can be orders of magnitude faster than doing nothing. Only multi-level conjugate gradient preconditioner (MULTI_LEVEL) available for AO response solver (AO_ORTHO). [Edit on GitHub]

Valid values:

FULL_ALL Most effective state selective preconditioner based on diagonalization, requires the ENERGY_GAP parameter to be an underestimate of the HOMO-LUMO gap. This preconditioner is recommended for almost all systems, except very large systems where make_preconditioner would dominate the total computational cost.
FULL_SINGLE_INVERSE Based on H-eS cholesky inversion, similar to FULL_SINGLE in preconditioning efficiency but cheaper to construct, might be somewhat less robust. Recommended for large systems.
FULL_SINGLE Based on H-eS diagonalisation, not as good as FULL_ALL, but somewhat cheaper to apply.
FULL_KINETIC Cholesky inversion of S and T, fast construction, robust, and relatively good, use for very large systems.
FULL_S_INVERSE Cholesky inversion of S, not as good as FULL_KINETIC, yet equally expensive.
MULTI_LEVEL Based on same CG as AO-solver itself, but uses cheaper linear transformation
NONE skip preconditioning

RESTART

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Type: logical
Default: F
Lone keyword: T
Usage: RESTART

Description: Restart the response calculation if the restart file exists [Edit on GitHub]

RESTART_EVERY

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Type: integer
Default: 50
Usage: RESTART_EVERY 50

Description: Restart the conjugate gradient after the specified number of iterations. [Edit on GitHub]

S_INVERSION

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Type: enum
Default: SIGN_SQRT
Usage: S_INVERSION MOLECULAR

Description: Method used to compute the inverse of S. [Edit on GitHub]

Valid values:

SIGN_SQRT Using the inverse sqrt as obtained from sign function iterations.
HOTELLING Using the Hotellign iteration.

S_PRECONDITIONER

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Type: enum
Default: ATOMIC
Usage: S_PRECONDITIONER MOLECULAR

Description: Preconditions S with some appropriate form. [Edit on GitHub]

Valid values:

NONE No preconditioner
ATOMIC Using atomic blocks
MOLECULAR Using molecular sub-blocks. Recommended if molecules are defined and not too large.

S_SQRT_METHOD

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Type: enum
Default: NEWTONSCHULZ
Usage: S_SQRT_METHOD NEWTONSCHULZ

Description: Method for the caclulation of the sqrt of S. [Edit on GitHub]

Valid values:

NEWTONSCHULZ Using a Newton-Schulz-like iteration
PROOT Using the p-th root method.

S_SQRT_ORDER

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Type: integer
Default: 3
Aliases: SIGN_SQRT_ORDER
Usage: S_SQRT_ORDER 3

Description: Order of the iteration method for the calculation of the sqrt of S. [Edit on GitHub]