ORCA¶
ORCA is a computational chemistry code that can do SCF, (TD)DFT, semi-empirical potentials, MP2, CASSCF, Coupled Cluster calculations, and more.
It is closed source, but free for academic users. Register on the forum to receive a download link for the binaries, as well as access to the latest manual.
Many input examples are available at the ORCA Input Library.
The ORCA ASE-interface is very simple. Two keywords are defined:
orcasimpleinput: str
What you'd put after the "!" in an orca input file.
orcablocks: str
What you'd put in the "% ... end"-blocks.
The ASE-calculator also works with the
EIQMMM-calculator
for QM/MM simulations (see qmmm for
more info).
Setup and usage¶
The default command that ASE will use to start ORCA is
orca PREFIX.inp > PREFIX.out.
For parallel calculations, you will need to specify the full path to the ORCA
executable. This can be done by defining an OrcaProfile like the example below:
from ase.calculators.orca import OrcaProfile
MyOrcaProfile = OrcaProfile(["/full/path/to/my/orca"])
calc = ORCA(profile=MyOrcaProfile)
ORCA decides which sub-processes to parallelize via MPI by itself, so you’ll
almost always want a string in your orcablocks specifying the number of
cores for the simulation, e.g.:
from ase.calculators.orca import ORCA
calc = ORCA(profile=MyOrcaProfile,
orcasimpleinput='B3LYP def2-TZVP'
orcablocks='%pal nprocs 16 end')
for a B3LYP/def2-TZVP calculation on 16 cores.
Class Definition¶
- class ase.calculators.orca.ORCA(*, profile=None, directory='.', parallel_info=None, parallel=None, **kwargs)[source]¶
Class for doing ORCA calculations.
Example
- calc = ORCA(charge=0, mult=1, orcasimpleinput=’B3LYP def2-TZVP’,
orcablocks=’%pal nprocs 16 end’)
Construct ORCA-calculator object.
Examples
Use default values:
>>> from ase.calculators.orca import ORCA >>> h = Atoms( ... 'H', ... calculator=ORCA( ... charge=0, ... mult=1, ... directory='water', ... orcasimpleinput='B3LYP def2-TZVP', ... orcablocks='%pal nprocs 16 end'))