Replica exchange¶

job = replica_exchange reads pos.con. It writes results.dat and the coldest replica as pos_out.con.

[Replica Exchange] replicas defaults to 10. temperature_distribution is exponential (the default) or linear. Any other value stops the job. temperature_low defaults to [Main] temperature. A low temperature that is not positive is replaced by [Main] temperature, or by 300 K when that temperature is not positive either. When temperature_high is not above temperature_low, the job sets it to 1.5 times temperature_low.

sampling_time (default 1000) and exchange_period (default 100) are in femtoseconds. The integrator step is [Dynamics] time_step. When thermostat is omitted, the client uses andersen.

At each exchange period the job proposes one swap per replica, between neighboring temperatures. After the file is read, exchange_trials is set equal to replicas, so the key does not change that count. A proposed swap of energies E_high and E_low is accepted with probability

\[\min\left(1, \exp\left[(E_{high}-E_{low})\left(\frac{1}{k_B T_{high}}-\frac{1}{k_B T_{low}}\right)\right]\right).\]

[Main]
job = replica_exchange
temperature = 300

[Replica Exchange]
replicas = 8
temperature_distribution = exponential
temperature_low = 300
temperature_high = 600
sampling_time = 1000
exchange_period = 100

[Dynamics]
time_step = 1.0
thermostat = langevin