Interface orca

Interface to the Orca package (https://orcaforum.cec.mpg.de/, free license for academic use). The interface was developed for version 2.9 and tested to work with 3.0.2. There are some changes in the input for Orca 4.0 and the interface was not tested thoroughly with this version.

Orca provides access to wide range of DFT and ab initio methods, both DFT and correled calculations can used the Resolution of identity approximation.

HF-3c and PBEh-3C

Orca implements small-basis HF/DFT calculations with the 3c corrections. The 3c stands for three corrrections for 1) dispersion, 2) basis set superposition error and 3) additional basis set incompleteness effects. Two versions are available, HF-3c based on Hartree-Fock calculation in minimal basis set[1] and PBEh-3c based on DFT in a double-zeta basis.[2] Using these methods activates the complete setup including the basis set for which the corrections were developed, no further setup is needed – see the example below.

Non-standard behavior

References

  1. R. Sure, S. Grimme, J. Comput. Chem., 2013, 34, 1672-1685
  2. S. Grimme, J. G. Brandenburg, C. Bannwarth, A. Hansen, The Journal of Chemical Physics, 2015, 143, 054107

Methods and capabilities

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

The interface implements following solvent models (keyword 'solvent_model'):

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/orca/examples

#===============================================================================
# Orca example 1: setup, HF calculation
#===============================================================================

# Simple input for HF calculation, all other options use default values.

job: energy
interface: orca

method: hf
basisset: cc-pVDZ

geometry: A24:water # Water molecule from the internal database
charge: 0

#-------------------------------------------------------------------------------
# Interface configuration
#-------------------------------------------------------------------------------
# Path to Orca binaries
orca_bin_dir: /home/rezac/bin/orca/orca-3.0.2/arch/amd64/orca_3_0_2_linux_x86-64

# The following examples assume that the interface is set up in the config file.

#===============================================================================
# Orca example 2: DFT and RI-DFT calculation
#===============================================================================

# Multistep protocol is used to run two calculations from one input
job: multistep 
steps: dft, ridft

calculation_dft:
  job: energy
  interface: orca
  
  method: dft
  functional: b-lyp
  basisset: SV
  density_fitting: none # disable RI (by default, it is enabled)

  geometry: A24:water
  charge: 0

calculation_ridft:
  job: energy
  interface: orca
  
  method: dft
  functional: b-lyp
  basisset: SV
  density_fitting: scf # enable RI (not necessary, enabled by default)
  auxiliary_basis_scf: SV # Auxiliary basis for RI has to be specified

  geometry: A24:water
  charge: 0


#===============================================================================
# Orca example 3: MP2 and RI-MP2 calculation
#===============================================================================

# Multistep protocol is used to run two calculations from one input
job: multistep 
steps: mp2, rimp2

# In contrast to the previous example, we gather the setup used in all steps
# into a common subsection:
calculation_common:
  job: energy
  interface: orca
  method: mp2
  basisset: cc-pVTZ
  geometry: A24:water
  charge: 0

calculation_mp2:
  density_fitting: none # disable RI (by default, it is enabled)

calculation_rimp2:
  density_fitting: correlation # enable RI (not necessary, enabled by default)
  auxiliary_basis_mp2: cc-pVTZ # Auxiliary basis for RI has to be specified

#===============================================================================
# Orca example 4: CCSD(T) calculation
#===============================================================================

job: energy
interface: orca

method: ccsd(t)
basisset: cc-pVDZ

geometry: A24:water # Water molecule from the internal database
charge: 0

# Print components of the CCSD(T) energy
print: energy_decomposition

# Other options affecting this calculation
correlation_frozen_core: yes # Frozen-core approximation, on by default
scf_convergence: 8 # For CCSD(T), we set tighter SCF convergence, default is 7



#===============================================================================
# Orca example 5: DLPNO-CCSD(T) calculation
#===============================================================================

# Approximate CCSD(T) calculation applicable to large systems - 
# Domain-Localized Pair Natural Orbitals CSCD(T)

job: energy
interface: orca

method: ccsd(t)
basisset: cc-pVDZ

geometry: A24:water # Water molecule from the internal database
charge: 0

# Print components of the CCSD(T) energy
print: energy_decomposition

# Setup needed in addition to plain CCSD(T)
orca_dlpno: yes # enable the approximation
auxiliary_basis_mp2: cc-pVDZ # Auxiliary basis for RI-MP2 is needed


#===============================================================================
# Orca example 6: HF-3c calculation
#===============================================================================

# The HF-3c method, a Hartree-foc calculation in minimal basis with corrections
# for basis set incompleteness and dispersion.

job: energy
interface: orca

# When the 3c methods are used, no setup besides the selection of the method
# is needed
method: hf-3c

# System specification: water molecule
geometry: A24:water
charge: 0