# CCLAMBDA

Solves for the Lagrange multipliers, which are needed whenever coupled cluster properties or gradients are requested.

## General

### ABCD

> Type of ABCD algorithm will be used

> - Type: string
> - Default: NEW

### AO_BASIS

> The algorithm to use for the \(\left\langle VV||VV \right\rangle\) terms

> - Type: string
> - Possible Values: NONE, DISK, DIRECT
> - Default: NONE

### CACHELEVEL

> Caching level for libdpd governing the storage of amplitudes, integrals, and intermediates in the CC procedure. A value of 0 retains no quantities in cache, while a level of 6 attempts to store all quantities in cache. For particularly large calculations, a value of 0 may help with certain types of memory problems. The default is 2, which means that all four-index quantities with up to two virtual-orbital indices (e.g., \(\left\langle ij | ab \right\rangle\) integrals) may be held in the cache.

> - Type: integer
> - Default: 2

### DIIS

> Do use DIIS extrapolation to accelerate convergence?

> - Type: boolean
> - Default: true

### LOCAL

> Do simulate the effects of local correlation techniques?

> - 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: 0.02

### LOCAL_FILTER_SINGLES

> Do apply local filtering to single de-excitation (\(\lambda 1\) amplitudes?

> - Type: boolean
> - Default: true

### 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: No Default

### 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

> - 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: 10

### PROP_ALL

> Compute unrelaxed properties for all excited states.

> - Type: boolean
> - Default: true

### PROP_ROOT

> Root number (within its irrep) for computing properties

> - Type: integer
> - Default: 1

### PROP_SYM

> The symmetry of states

> - Type: integer
> - Default: 1

### RESTART

> Do restart the coupled-cluster iterations from old \(\lambda_1\) and \(\lambda_2\) amplitudes?

> - Type: boolean
> - Default: false

### ROOTS_PER_IRREP

> The number of electronic states to computed, per irreducible representation

> - Type: array
> - Default: No Default

### R_CONVERGENCE

> Convergence criterion for wavefunction (change) in CC lambda-amplitude equations.

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

### SEKINO

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

> - Type: boolean
> - Default: false

### ZETA

> Do use zeta?

> - Type: boolean
> - Default: false

## Expert

### JOBTYPE

> Type of job being performed

> - Type: string
> - Default: No Default

### WFN

> Wavefunction type

> - Type: string
> - Default: SCF