# CCHBAR

Assembles the coupled cluster effective Hamiltonian. Called whenever CC properties and/or gradients are required.

## General

### 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., \(\langle ij | ab \rangle\) integrals) may be held in the cache.

> - Type: integer
> - Default: 2

### EOM_REFERENCE

> Reference wavefunction type for EOM computations

> - Type: string
> - Default: RHF

### T_AMPS

> Do compute the T amplitude equation matrix elements?

> - Type: boolean
> - Default: false

### WABEI_LOWDISK

> Do use the minimal-disk algorithm for Wabei? It’s VERY slow!

> - Type: boolean
> - Default: false

## Expert

### WFN

> Wavefunction type

> - Type: string
> - Default: SCF