# QMMM Dynamics

### From NWChem

Dynamical simulations within QM/MM framework can be initiated using

task qmmm <qmtheory> dynamics

directive. User has to specify the region for which simulation will performed. If dynamics is performed only for the classical parts of the system (QM region is fixed) then ESP point charge representation (density espfit) is recommended to speed up simulations. If this option is utilized then wavefunction file (<system>.movecs) has to be available and present in the permanent directory (this can be most easily achieved by running energy calculation prior to dynamics).

Example input file for QM/MM classical solvent dynamics. QM region is fixed and represented by ESP point charges. Prior to dynamics the wavefunction is generated by running total energy calculation. Constant temperature ensemble is used (see isotherm directive in the md block). Note that the wtr_dyn.rst will be overwritten with new coordinates/velocities at the end of the calculation.

start wtr permanent_dir ./perm scratch_dir ./data md system wtr_dyn data 100 isotherm print step 1 stat 10 end basis * library "6-31G" end dft xc b3lyp end qmmm region solvent density espfit end task qmmm dft energy task qmmm dft dynamics