ECV_MULTITHERMAL_MULTIBARIC

	This is part of the opes module
	It is only available if you configure PLUMED with ./configure –enable-modules=opes . Furthermore, this feature is still being developed so take care when using it and report any problems on the mailing list.

Expand a simulation to sample multiple temperatures and pressures.

The potential ENERGY, \(E\), and the VOLUME, \(V\), of the system should be used as ARG.

\[ \Delta u_{\beta',p'}=(\beta'-\beta) E + (\beta' p' -\beta p) V\, , \]

where \(\beta', p'\) are the temperatures and pressures to be sampled, while \(\beta, p\) is the temperature and pressure at which the simulation is conducted.

If instead you wish to sample multiple temperatures and a single pressure, you should use ECV_MULTITHERMAL with as ARG the internal energy \(U=E+pV\).

The TEMP_STEPS and PRESSURE_STEPS are automatically guessed from the initial unbiased steps (see OBSERVATION_STEPS in OPES_EXPANDED), unless explicitly set. The algorithm for this guess is described in [75] should provide a rough estimate useful for most applications. The pressures are uniformely spaced, while the temperatures steps are geometrically spaced. Use instead the keyword NO_GEOM_SPACING for a linear spacing in inverse temperature (beta). For more detailed control you can use instead TEMP_SET_ALL and/or PRESSURE_SET_ALL to explicitly set all of them. The temperatures and pressures are then combined in a 2D grid.

You can use CUT_CORNER to avoid a high-temperature/low-pressure region. This can be useful e.g. to increase the temperature for greater ergodicity, while avoiding water to vaporize, as in Ref.[75].

You can reweight the resulting simulation at any temperature and pressure in chosen target, using e.g. REWEIGHT_TEMP_PRESS. A similar target distribution can be sampled using TD_MULTITHERMAL_MULTIBARIC.

Examples

Click on the labels of the actions for more information on what each action computes

ene: ENERGY The ENERGY action with label ene calculates a single scalar value
vol: VOLUME The VOLUME action with label vol calculates a single scalar value
ecv: ECV_MULTITHERMAL_MULTIBARIC ...
   ARGcompulsory keyword 
the labels of the potential energy and of the volume of the system. =ene,vol 
   TEMPcompulsory keyword ( default=-1 )
temperature. =500 
   TEMP_MINthe minimum of the temperature range =270 
   TEMP_MAXthe maximum of the temperature range =800 
   PRESSUREcompulsory keyword 
pressure. =0.06022140857*2000 #2 kbar 
   PRESSURE_MINthe minimum of the pressure range =0.06022140857 #1 bar 
   PRESSURE_MAXthe maximum of the pressure range =0.06022140857*4000 #4 kbar 
   CUT_CORNERavoid region of high temperature and low pressure. =500,0.06022140857,800,0.06022140857*1000 
...The ECV_MULTITHERMAL_MULTIBARIC action with label ecv calculates the following quantities:

 Quantity   
 Description  
ecv.ene
the label of this action is set by user in the input. See documentation above.
ecv.vol
the label of this action is set by user in the input. See documentation above.


opes: OPES_EXPANDED ARGcompulsory keyword 
the label of the ECVs that define the expansion. =ecv.* FILEcompulsory keyword ( default=DELTAFS )
a file with the estimate of the relative Delta F for each component of the target
and of the global c(t) =DeltaF.data PACEcompulsory keyword 
how often the bias is updated =500 WALKERS_MPI( default=off ) switch on MPI version of multiple walkers  The OPES_EXPANDED action with label opes calculates a single scalar value

Notice that \(p=0.06022140857\) corresponds to 1 bar only when using the default PLUMED units. If you modify them via the UNITS command, then the pressure has to be rescaled accordingly.

Glossary of keywords and components

Compulsory keywords

TEMP	( default=-1 ) temperature. If not specified tries to get it from MD engine
ARG	the labels of the potential energy and of the volume of the system. You can calculate them with ENERGY and VOLUME respectively
PRESSURE	pressure. Use the proper units

Options

NUMERICAL_DERIVATIVES	( default=off ) calculate the derivatives for these quantities numerically
NO_GEOM_SPACING	( default=off ) do not use geometrical spacing in temperature, but instead linear spacing in inverse temperature
TEMP_MIN	the minimum of the temperature range
TEMP_MAX	the maximum of the temperature range
TEMP_STEPS	the number of steps in temperature
TEMP_SET_ALL	manually set all the temperatures
PRESSURE_MIN	the minimum of the pressure range
PRESSURE_MAX	the maximum of the pressure range
PRESSURE_STEPS	the number of steps in pressure
PRESSURE_SET_ALL	manually set all the pressures
SET_ALL_TEMP_PRESSURE	manually set all the target temperature_pressure pairs. An underscore separates temperature and pressure, while different points are comma-separated, e.g.: temp1_pres1,temp1_pres2,...
CUT_CORNER	avoid region of high temperature and low pressure. Exclude all points below a line in the temperature-pressure plane, defined by two points: \(T_{\text{low}},P_{\text{low}},T_{\text{high}},P_{\text{high}}\)