THERMOS

NAME
THERMOS - Run with Nosé thermostats for NVT or NPT simulations.

SYNOPSIS

 
  THERMOS
     ...
  END

DESCRIPTION
For a faster and better energy equipartition, ORAC uses three thermostats. The first,coupled to the center of mass momenta of all molecules in the system, the second coupled to the momenta of the atoms of the solute (if present) and the third coupled to the momenta of solvent atoms (if present). The following subcommands may be specified within THERMOS:

cofm, defaults,solute, solvent, temp_limit

$\bullet$

cofm    freq_mass   
Specify the mass of the barostat coupled to the centers of mass of the molecules. This mass is also assigned to the barostat coupled to the box momenta in NPT simulation, in case STRESS or ISOSTRESS have been specified. Actually, what is entered with the variable freq_mass is the (approximate) frequency of oscillation of the thermostat. The actual ``mass'' $W$ (in units of mass times a length to the power of two) of the barostat may be recovered according to the relation ${\it freq\_mass} = (2Nk_{B} T /W)^{1/2}$.[80]

$\bullet$

defaults
Use defaults value for ``mass'' variables. The defaults are freq_mass_solute = freq_mass_solvent freq_mass = 30.0.

$\bullet$

solute    freq_mass_solute
Specify mass (units of cm$^-1$) of the barostat coupled to the momenta of the solute atoms.

$\bullet$

solvent    freq_mass_solvent
Specify mass (units of cm$^-1$) of the barostat coupled to the momenta of the solvent atoms.

$\bullet$

temp_limit    maxtemp
Specify maximum temperature allowed for all Nosé thermostat when the argument of the command REJECT(&RUN) is different from zero. In principle, for a system out of equilibrium, no temperature scaling should be enforced when using Nosé thermostatting. Actually, when equilibrating systems in the NVT or NPT ensembles, it is strongly recommended to specify the subcommand temp_limit along with a rejection time REJECT(&RUN) as normally done for conventional scaling in NVE dynamics. In a NV(P)T system out of equilibrium, while the temperature of the system remains close to the selected temperature, the temperature of the thermostat coordinates (which are not themselves thermostatted) may raise dramatically, if not scaled.

EXAMPLES

 
&SIMULATION 
  TEMPERATURE 300.0 25.0 
  MDSIM 
  THERMOS 
    cofm 30.0 
    solute 30.0 
    solvent 30.0 
  END
&END

Run a simulation in the NVT ensemble at T = 300 K.