MOPAC COSMO calculation¶

Here it is described briefly how to make MOPAC COSMO result files.

The simplest way is to use ADFinput. Draw the molecule using ADFinput, and save the .adf file. Select Right Panel → MOPAC → Solvation method → COSMO-CRS. Press Run to run the MOPAC calculation. A .coskf file will be saved that can be used as input in COSMO-RS calculations.

Technically ADFinput will add some keywords to the input for MOPAC (see also http://www.openmopac.net). The main input keys for MOPAC that are used are:

PM6 EPS=9999.9 RSOLV=1.3 COSWRT NSPA=362

The use of COSWRT makes MOPAC create a .cos file, which is converted to a .coskf file by $ADFBIN/cosmo2kf

cosmo2kf file.cos file.coskf

Note that this is automatically done if one uses ADFinput.

Compared to the default ADF COSMO-RS values a few COSMO-RS parameters were reoptimized for MOPAC PM6 COSMO result files to improve the calculation of a number of partition coefficients, when compared to experimental values. Note that MOPAC is a semi-empirical quantum chemistry program, whereas ADF is based on density functional theory (DFT). Thus the MOPAC COSMO result files will not be of the same quality as the ADF COSMO result files.