fix grem command
Syntax
fix ID group-ID grem lambda eta H0 thermostat-ID
ID, group-ID are documented in fix command
grem = style name of this fix command
lambda = intercept parameter of linear effective temperature function
eta = slope parameter of linear effective temperature function
H0 = shift parameter of linear effective temperature function
thermostat-ID = ID of Nose-Hoover thermostat or barostat used in simulation
Examples
fix fxgREM all grem 400 -0.01 -30000 fxnpt
thermo_modify press fxgREM_press
fix fxgREM all grem 502 -0.15 -80000 fxnvt
Description
This fix implements the molecular dynamics version of the generalized replica exchange method (gREM) originally developed by (Kim), which uses non-Boltzmann ensembles to sample over first order phase transitions. The is done by defining replicas with an enthalpy dependent effective temperature
with
This fix requires a Nose-Hoover thermostat fix reference passed to the grem as thermostat-ID. Two distinct temperatures exist in this generalized ensemble, the effective temperature defined above, and a kinetic temperature that controls the velocity distribution of particles as usual. Either constant volume or constant pressure algorithms can be used.
The fix enforces a generalized ensemble in a single replica
only. Typically, this ideology is combined with replica exchange with
replicas differing by
In general, defining the generalized ensembles is unique for every
system. When starting a many-replica simulation without any knowledge
of the underlying microcanonical temperature, there are several tricks
we have utilized to optimize the process. Choosing a less-steep
Restart, fix_modify, output, run start/stop, minimize info
No information about this fix is written to binary restart files.
The thermo_modify press option is supported by this fix to add the rescaled kinetic pressure as part of thermodynamic output.
This fix computes a global scalar which can be accessed by various
output commands. The scalar is the effective
temperature
Restrictions
This fix is part of the REPLICA package. It is only enabled if LAMMPS was built with that package. See the Build package page for more info.
Default
none
(Kim) Kim, Keyes, Straub, J Chem. Phys, 132, 224107 (2010).
(Malolepsza) Malolepsza, Secor, Keyes, J Phys Chem B 119 (42), 13379-13384 (2015).