Interface cfour

Interface to the CFOUR program package (, free for academic use). CFOUR (Coupled-Cluster techniques for Computational Chemistry) package implements high-level QM calculations. An important feature is the availability of analytic first and second energy derivatives for the coupled clusters methods.

The interface was developed and tested with version 1 of CFOUR. For CCSD and CCSD(T) calculations, externally provided MRCC program can be used.

Methods and capabilities

The interface implements following methods (specified by keyword 'method'):

Keywords used

Keywords specific for this interface:

Other keywords used by this interface:


The following examples, along with all other files needed to run them, can be found in the directory cuby4/interfaces/cfour/examples

# CFOUR example 1: optimization and vibrational analysis at CCSD(T) level

# Optimization and vibrational frequencies calculation of water molecule
# at CCSD(T) level (small basis set is used to make the example run fast)
# CFOUR is one of very few codes that calculate the energy derivatives
# at CCSD(T) level analytically.

# The Multistep protocl is used to run the optimization and frequency
# calculations in one input file
job: multistep
steps: optimization, frequencies

# Optimization step
  job: optimize
  opt_quality: 0.1
  geometry: |
    O   -0.702196054  -0.056060256   0.009942262
    H   -1.022193224   0.846775782  -0.011488714
    H    0.257521062   0.042121496   0.005218999

# Frequencies calculation
  job: frequencies
  geometry: # Read the optimized geometry from the previous step

# Common setup
# The method is the same in both steps, CFOUR interface is used

  # The following setup is shared by all the steps
  interface: cfour
  method: ccsd(t)
  basisset: 6-31G
  charge: 0

# Interface configuration
# Minimal setup needed for serial calculations

# Path to CFOUR binaries
cfour_bin_dir: /home/rezac/bin/cfour/cfour_v1_64bit/bin
# Path to the GENBAS file containg basis sets
cfour_genbas_file: /home/rezac/bin/GENBAS