multi_replica remd

This command selects temperature replica-exchange molecular dynamics (REMD) [Sugita1999].

Syntax

multi_replica remd replicas <number> [<per_gpu>] exchange <interval> temp <T_min> <T_max> [spacing <type>] [equilibrate <steps>] [resume <prefix>]

  • number: at least two replicas; see multi_replica for GPU allocation.

  • exchange: positive number of MD steps between exchange rounds.

  • temp: positive ladder endpoints in K, with T_min < T_max. Alternatively, use temp <filename> to read a temperature file.

  • spacing: geometric (default) or linear for generated ladders.

  • equilibrate: independent NVT steps before exchanges begin; default 0. These steps do not count toward run.

  • resume: restart prefix; cannot be combined with positive equilibrate.

Example

multi_replica remd replicas 8 exchange 1000 temp 300 450 equilibrate 200000

A complete input is shown in Simulation protocol (run.in).

Caveats

  • Exchanges alternate between adjacent temperature-label pairs, starting with (0, 1), (2, 3), .... For two replicas, the only pair is attempted every round.

  • Accepted exchanges swap temperature assignments and rescale velocities; coordinates remain with their replica. Collect fixed-temperature statistics by temperature label, not replica index.