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