Advanced molecular dynamics parameters

ensemble type

Users can choose between the micro-canonical (constant electronic energy) and the canonical (constant temperature) ensembles. The micro-canonical ensemble is integrated with the velocity Verlet algorithm. The canonical ensemble via Nose'-Hoover dynamics is integrated with a generalized leap frog method (J. Comp. Phys. 151 p.114 (1999).

ensemble_type default=2            1 - constant energy
                                   2 - constant temperature via Nose'-Hoover dynamics

extrapolation methods - for relaxation also

In order to minimize the number of updates to the electronic wavefunctions in order to reach convergence, an extrapolation of the wavefunctions and/or potential is done to obtain better initial guess for each atomic configuration. One can choose between a first order, 2nd order (PRB 45 p1538 (1992)), or an alternating sequence of these two methods.

  < 0             No extrapolation.
    0             1st order extrapolation of wavefunctions and
                  potential
    1             2nd order extrapolation of wavefunctions and
                  potential
    2             alternating extrapolation of wavefunctions and
                  potential
   10             1st order extrapolation of wavefunctions and
                  potential is created from extrapolated
                  wavefunctions - suggested for direct
                  minimization methods
   11             2nd order extrapolation of wavefunctions and
                  potential same as 10
   12             alternating extrapolation of wavefunctions and
                  potential same as 10

extrapolation_method  (default 2 -MD) (default 1 - for relaxation)

Mass of extended system for canonical ensemble

For the Nose'-Hoover dynamics, a mass is specified for the extended system that acts as a heat bath in order to regulate the temperature of the electronic and ionic system. A very small or large value will result in non-canonical behavior. The mass is entered in units of Rydbergs. An overall energy of the electrons, ions, and the extended system is conserved.

MD_Q_mass default(= total thermal energy / 10)   value in Rydbergs