Interface psi4

Interface to the Psi4 quantum chemistry package (www.psicode.org, open source). Psi4 offers modern implementation of wide range of QM methods.

For now, the interface provides access to the basic wavefunction QM methods (including the FNO approximation) and to SAPT.

Methods and capabilities

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

hf - supports calculation of energy, gradient, hessian
dft - supports calculation of energy, gradient, native_opt, hessian
mp2 - supports calculation of energy, gradient, native_opt, hessian
mp3 - supports calculation of energy, gradient, native_opt, hessian
ccsd - supports calculation of energy
ccsd(t) - supports calculation of energy
sapt - supports calculation of energy

Input structure

Optionally, following blocks can be defined in the input:

molecule_a - Definition of the first monomer for SAPT calculation (selection, charge, multiplicity)
molecule_b - Definition of the second monomer for SAPT calculation (selection, charge, multiplicity)

Keywords used

Keywords specific for this interface:

Other keywords used by this interface:

Examples

The following examples, along with all other files needed to run them, can be found in the directory cuby4/interfaces/psi4/examples

#===============================================================================
# Psi4 interface example 1 - interface configuration
#===============================================================================

# The following keyword is needed to configure the interface -
# path to the directory containing Psi4 binaries:
psi4_bin_dir: /home/rezac/bin/psi4/install/bin

# The following examples assume that this keyword is set in the global
# configuation file.

# Let's try some calculation - MP2 with desity fitting
job: energy
interface: psi4

geometry: A24:water
charge: 0

method: mp2
density_fitting: both # DF-HF + DF-MP2
basisset: "6-31G"

#===============================================================================
# Psi4 interface example 2 - FNO-CCSD(T)
#===============================================================================

# The Frozen Natural Orbitals approximation can be used to accelerate
# CCSD and CCSD(T) calculations.

job: energy
interface: psi4

geometry: A24:water
charge: 0

method: ccsd(t)
basisset: cc-pVDZ

# Use density fitting where possible, switch on the FNO approximation:
density_fitting: both
psi4_fno: yes

#===============================================================================
# Psi4 interface example 3 - SAPT
#===============================================================================

# This input demonstrates how to run a SAPT calculation, it requires some
# specific input.

interface: psi4

# Although interaction energy is calculated, it is done in a single run of
# the external program, called by the "energy" protocol
job: energy

geometry: S66:water_dimer # Water dimer from the S66 data set
charge: 0

method: sapt
# Order of the SAPT expansion - SAPT0 is the most approximate level available:
psi4_sapt_level: sapt0

basisset: aug-cc-pVDZ
density_fitting: both

# The information on the fragments (monomers) to be passed to Psi4:
psi4_geometry_fragments: yes
molecule_a:
  charge: 0
  multiplicity: 1
  selection: "1-3"
molecule_b:
  charge: 0
  multiplicity: 1
  selection: "4-6"

# To get the components of the interaction energy, enable their printing:
print: energy_decomposition