Constrained molecular dynamics

1. define the standard MD-related parameters: IBRION=0, TEBEG, POTIM, NSW
2. set MDALGO to 1 or 2 for a simulation with Andersen, or Nose-Hoover thermostat, respectively (check description of ANDERSEN_PROB and SMASS for the thermostat-specific setting)
3. define geometric constraints in file ICONST (see Sec. 6.62.4), the input parameter STATUS for constrained coordinates must be set to 0
4. if the free-energy gradient is to be computed, set LBLUEOUT=.TRUE., see Sec. 6.62.3

VASP can handle multiple (even redundant) constraints, note however that a too large number of constraints can cause problems with the stability of the SHAKE algorithm. In the problematic cases, it is recommended to use a looser convergence criterion and to allow a larger number of iterations in the SHAKE algorithm (see Sec. 6.62.3). The hard constraints can be used also in metadynamics simulations (MDALGO=11$\vert$21). Information about constraints is written in file REPORT, check the lines following the string "Const_coord".