Coupled Cluster



Wave function object for Restricted Coupled Cluster Singles and Doubles.

High Level Interface

Run a RCCSD computation and return the RCCSD object:

julia> @energy rccsd 

Equivalent to

julia> Fermi.CoupledCluster.RCCSD()

This function calls a constructor that runs a RCCSD computation based on the options found in Fermi.Options.


guessenergyEnergy recovered in the first iteration, normally RMP2
correlationComputed RCCSD correlation energy
energyTotal wave function energy (Reference energy + Correlation energy)
e_convΔE from the last iteration
t_convAmplitudes RMS change from the last iteration

Relevant options

These options can be set with @set <option> <value>

OptionWhat it doesTypechoices [default]
cc_algPicks RCCSD algorithmInt[1]
cc_e_convEnergy convergence criterionFloat64[10^-10]
cc_max_rmsAmplitudes RMS convergence criterionFloat64[10^-10]
cc_max_iterMax number of CC iterationsInt[50]
cc_damp_ratioFraction of old amplitudes to be keptFloat640.0–1.0 [0.0]
cc_diisWhether to use DIISBoolfalse [true]
diis_startIteration number where DIIS startsInt[3]
cc_diis_relaxInterval between DIIS extrapolationsInt[3]
cc_ndiisMaximum number of stored vectors for DIISInt[3]
basisWhat basis set to useString["sto-3g"]
dfWhether to use density fittingBooltrue [false]
rifitWhat aux. basis set to use for RIString["auto"]
drop_occNumber of occupied electrons to be droppedInt[0]
drop_virNumber of virtual electrons to be droppedInt[0]



Fermi struct that holds information about RCCSD(T) wavefunctions

struct tree:

RCCSD(T) <: AbstractCCWavefunction <: AbstractCorrelatedWavefunction <: AbstractWavefunction