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Stochastic boundary conditions

See Sec. 6.62.5 and 6.62.5 for brief
description of stochastic boundary conditions and Langevin thermostat, respectively.
Note that geometric constraints and metadynamics are not
supported for this simulation protocol.
- Set the standard MD-related flags:
`IBRION=0`, `TEBEG`, `POTIM`, `NSW`,
`ISIF=2`
- Set
`MDALGO` to 3 to invoke Langevin dynamics 6.62.3.
- Prepare the
`POSCAR` file in such a way that the Newtonian and Langevin
atoms are treated as different species (even if they are chemically identical)
- In
`POSCAR`, use Selective Dynamics and corresponding logical flags to
define the frozen and movable atoms
- Using
`LANGEVIN_GAMMA` (see 6.62.3), set friction coefficients () to zero for all
fixed and Newtonian atoms, use proper value of for Langevin atoms

N.B. Requests for support are to be addressed to: vasp.materialphysik@univie.ac.at