# 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

> Caching 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. For polarizability, this keyword is ignored and `LENGTH` gauge is computed. For optical rotation and raman optical activity, this keyword is active, and acceptable values are `LENGTH` for the usual length-gauge representation, `VELOCITY``(default) 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 and raman optical activity calculations, only the choices of `VELOCITY` or `BOTH` will yield origin-independent results.

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

### 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 available 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 available 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

> The response property desired. Acceptable values are `POLARIZABILITY` (default) for dipole polarizabilities, `ROTATION` for specific rotations, `ROA` for Raman Optical Activity (`ROA_TENSOR` for each displacement), and `ALL` for all of the above.

> - Type: string
> - Possible Values: POLARIZABILITY, ROTATION, ROA, ROA_TENSOR, 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