Import EPR properties from ORCA output file.

Sys = orca2easyspin(OrcaFileName)
... = orca2easyspin(OrcaFileName,hfCutoff)

See also the user guide that describes the ORCA-EasySpin interface.

This function loads EPR properties calculated by ORCA. ORCA is a quantum chemistry program with extensive support for the calculation of EPR properties such as the g tensor, the zero-field splitting tensor, hyperfine tensors, and electric field gradients for nuclear quadrupole tensors.

OrcaFileName is the filename, including extension, of the main output file generated by ORCA.

For ORCA versions prior to 5, a binary property output file with the extension .prop is also provided by ORCA and can be used with orca2easyspin. There is no significant difference, or advantage, of using the property file compared to using the main output file. The text-based property output file with extension _property.txt provided starting from ORCA version 5, and containing calculated properties in a condensed format compared to the main output file, can currently not be used to load data into EasySpin, the main output file should be used instead.

Sys is an EasySpin spin system structure containing all the spin Hamiltonian EPR parameters calculated by ORCA. Assuming all EPR properties of the spin system have been calculated by ORCA, only line broadenings need to be added to be ready for an EPR spectral simulation.

In addition to the spin Hamiltonian parameters Sys also contains additional information imported from ORCA, such as a list of atom coordinates, a list of element numbers.

The field Sys.NucsIdx list the atom index for every nucleus listed in Sys.Nucs. For example, if Sys.Nucs='H' and Sys.NucsIdx=7, this indicates that the hydrogen is atom number 7.

hfCutoff, if given, specifies a cutoff level for hyperfine couplings. Any atoms with hyperfine couplings equal to or smaller than hfCutoff (in MHz) will be omitted from the spin system. This is useful for large molecules, where many of the ORCA-calculated hyperfine couplings are small and would not be resolvable in an EPR spectrum.

To load a spin system from an ORCA calculation with results in molecule.out (main ORCA output text file) use the following:

Sys = orca2easyspin('molecule.out');   % loads spin system from main ORCA output file

To skip nuclei with hyperfine couplings less than 0.8 MHz, specify a second parameter:

Sys = orca2easyspin('molecule.out',0.8);   % exclude nuclei with <=0.8 MHz hyperfine cut-off

In order to remove all nuclei except one or two of interest, use the function nucspinkeep:

Sys = orca2easyspin('molecule.out');   % load entire spin system from ORCA output
Sys = nucspinkeep(Sys,[1 2]);          % remove all nuclei except the first and the second

spin system structures, nucspinadd, nucspinkeep, nucspinrmv