Hi,

Just here for a general question - which qm software is most commonly used for qm/mm calculations.

I am using orca as the qm software which takes days and days to converge a qm/mm calculation with electrostatic embedding.

For a system of around 60 atoms it takes 3 days with basis set 6-31+g* and with around 115 atoms the job never converges.

Should I change my software or any different method I need to follow ?

Thank you.

Hi,

ORCA is widely used in biomolecular modelling and is usually a good choice as far as converging a calculation goes. It can be run in parallel with MPI and so the simplest way to speed up the calculation is to run it with more processor cores. If you find that ORCA's parallel scaling is insufficient, you could consider other packages which ChemShell interfaces to such as NWChem, which scale very well to large numbers of cores.

Best wishes,

Tom