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# CCRESPONSE

Performs SCF linear response computations.

## General

### ABCD

> Type of ABCD algorithm will be used

> - Type: string
> - Default: NEW

### ANALYZE

> Do analyze X2 amplitudes

> - Type: boolean
> - Default: false

### CACHELEVEL

> Cacheing level for libdpd

> - Type: integer
> - Default: 2

### DIIS

> Do use DIIS extrapolation to accelerate convergence?

> - Type: boolean
> - Default: true

### GAUGE

> Specifies the choice of representation of the electric dipole operator. Acceptable values are `LENGTH` for the usual length-gauge representation, `VELOCITY` for the modified velocity-gauge representation in which the static-limit optical rotation tensor is subtracted from the frequency- dependent tensor, or `BOTH`. Note that, for optical rotation calculations, only the choices of `VELOCITY` or `BOTH` will yield origin-independent results.

> - Type: string
> - Possible Values: LENGTH, VELOCITY, BOTH
> - Default: LENGTH

### LINEAR

> Do Bartlett size-extensive linear model?

> - Type: boolean
> - Default: false

### LOCAL

> Do simulate local correlation?

> - Type: boolean
> - Default: false

### LOCAL_CPHF_CUTOFF

> Cutoff value for local-coupled-perturbed-Hartree-Fock

> - Type: double
> - Default: 0.10

### LOCAL_CUTOFF

> Value (always between one and zero) for the Broughton-Pulay completeness check used to contruct orbital domains for local-CC calculations. See J. Broughton and P. Pulay, J. Comp. Chem. 14, 736-740 (1993) and C. Hampel and H.-J. Werner, J. Chem. Phys. 104, 6286-6297 (1996).

> - Type: double
> - Default: 0.01

### LOCAL_FILTER_SINGLES

> Do apply local filtering to single excitation amplitudes?

> - Type: boolean
> - Default: false

### LOCAL_METHOD

> Type of local-CCSD scheme to be simulated. `WERNER` (unique avaliable option) selects the method developed by H.-J. Werner and co-workers.

> - Type: string
> - Default: WERNER

### LOCAL_PAIRDEF

> Definition of local pair domains

> - Type: string
> - Default: NONE

### LOCAL_WEAKP

> Desired treatment of “weak pairs” in the local-CCSD method. The value of `NONE` (unique avaliable option) treats weak pairs in the same manner as strong pairs.

> - Type: string
> - Default: NONE

### MAXITER

> Maximum number of iterations to converge perturbed amplitude equations

> - Type: integer
> - Default: 50

### NUM_AMPS_PRINT

> Number of important CC amplitudes per excitation level to print. CC analog to NUM_DETS_PRINT

> - Type: integer
> - Default: 5

### OMEGA

> Array that specifies the desired frequencies of the incident// radiation field in CCLR calculations. If only one element is// given, the units will be assumed to be atomic units. If more// than one element is given, then the units must be specified as the final// element of the array. Acceptable units are `HZ`, `NM`, `EV`, and `AU`.

> - Type: array
> - Default: No Default

### PROPERTY

> Array that specifies the desired frequencies of the incident// radiation field in CCLR calculations. If only one element is// given, the units will be assumed to be atomic units. If more// than one element is given, then the units must be specified as the final// element of the array. Acceptable units are HZ, NM, EV, and AU.

> - Type: string
> - Possible Values: POLARIZABILITY, ROTATION, ROA, ALL
> - Default: POLARIZABILITY

### REFERENCE

> Reference wavefunction type

> - Type: string
> - Default: RHF

### RESTART

> Do restart from on-disk amplitudes?

> - Type: boolean
> - Default: true

### R_CONVERGENCE

> Convergence criterion for wavefunction (change) in perturbed CC equations.

> - Type: conv double
> - Default: 1e-7

### SEKINO

> Do Sekino-Bartlett size-extensive model-III?

> - Type: boolean
> - Default: false

## Expert

### WFN

> Wavefunction type

> - Type: string
> - Default: SCF

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