ensemble (TI_Spring)

This keyword is used to set up a nonequilibrium thermodynamic integration integrator. Please check [Freitas2016] for more details.

Syntax

The parameters can be specified as follows:

ensemble ti_spring temp <temperature> tperiod <tau_temperature> tequil <equilibrium_time> tswitch <switch_time> spring <element_name> <spring_constant>
  • <temperature>: The temperature of the simulation.

  • <tau_temperature>: This parameter is optional, and defaults to 100. It determines the period of the thermostat in units of the timestep. It determines how strongly the system is coupled to the thermostat.

  • <equilibrium_time>: The number timesteps to equilibrate the system.

  • <switch_time>: The number timesteps to vary lambda from 0 to 1.

  • <element_name> and <spring_constant>: Specify the spring constants of elements.

Please note that the spring constants should be placed at the end of the command.

Example

ensemble ti_spring temp 300 tequil 1000 tswitch 4000 spring Si 6 O 5

This command switch lambda for 4000 timesteps, and equilibrate for 1000 timesteps. The spring constant is 6 eV/A^2 for Si and 5 eV/A^2 for O.

Output file

This command will produce a csv file. The columns are lambda, dlambda, potential energy and spring energy (eV/atom).