6.11 Non-Iterative Corrections to Coupled Cluster Energies

6.11.5 Examples

(June 30, 2021)

Example 6.31  Two jobs that compare the correlation energy calculated via the standard CCSD(T) method with the new CCSD(2) approximation, both using the frozen core approximation. This requires that CC_INCL_CORE_CORR must be specified as FALSE in the CCSD(2) input.

$molecule
   0  2
   O
   H  O  0.97907
$end

$rem
   METHOD          ccsd(t)
   BASIS           cc-pvtz
   N_FROZEN_CORE   fc
$end

@@@

$molecule
   read
$end

$rem
   METHOD              ccsd(2)
   BASIS               cc-pvtz
   N_FROZEN_CORE       fc
   CC_INCL_CORE_CORR   false
$end

View output

Example 6.32  Using libpt for a standard CCSD(T) calculation

$molecule
   0  2
   O
   H  O  0.97907
$end

$rem
   METHOD          ccsd(t)
   BASIS           cc-pvtz
   N_FROZEN_CORE   fc
   USE_LIBPT       true
$end

View output