eos.tcl

::pwtk::eos::EOS

::pwtk::eos::EOS

SYNOPSIS

proc ::pwtk::eos::EOS {content} {

PURPOSE

The input data for the EOS calculation are specified with the EOS namelist. This proc is the implementation of the EOS namelist.

EOS = equation-of-state. EOS is a workflow for automatic determination of the "A" lattice parameter and bulk modulus. For non-cubic systems, only "A" is optimized keeping the cell shape intact, i.e., the ratio between A, B, C is maintained and angles are kept fixed.

BEWARE

All distances in the EOS namelist are specified in bohr units!

DESCRIPTION

A short description of the EOS namelist:

    EOS {
        mode = auto | range | stepwise
        npoints = integer-number
    
        use_estimator_points = .true. | .false. | yes | no | 1 | 0 | ... # any boolean value accepted by Tcl
    
        # if mode==auto
    
        a0 = real-number 
        B0  = 'high' | 'medium' | 'small' | real-number (in kbar)
        da0 = real-number
        scale_min = real-number
        scale_max = real-number
    
        # if mode==range
    
        amin = real-number (in Bohr units) [REQUIRED]
        amax = real-number (in Bohr units) [REQUIRED]
        use_stress = true | false (whether to use stress, default=true)
    
        # if mode==stepwise
    
        amin = real-number (in Bohr units) [REQUIRED]
        da = real-number (in Bohr units)   [REQUIRED]
        use_stress = true | false (whether to use stress, default=true)
    }

REMARK

Majority of variables in the EOS namelist are optional because reasonable default values are provided in the config/eos.tcl file.

Description of the EOS variables:

mode -- mode of the lattice parameter search [default=auto]. Possibilities are: auto, range, and stepwise
npoints -- number of single-point scf calculations
use_estimator_points -- whether to use the initial estimator points data in the final assessment (fitting) of the results
use_stress -- whether to use the stress via tstress=.true. in the CONTROL namelist (default=true)

mode == auto: lattice-parameter scanning range is automatically determined; "npoints" SCF calculations is performed in this range. The following optional variables may be specified:

a0 -- initial guess for the lattice parameter (in Bohr, default = celldm(1))
B0 -- initial guess for the bulk-modulus (in kbar); used only when a0 is substantially far from the minimum. Possible values are: "small", "medium", "high", or numeric value in kbar units.
da0 -- criterion for choosing the 2nd estimator point, a = a0*(1 +/- da0)
scale_min, scale_max -- scan the lattice parameter from scale_min*a0 to scale_max*a0, where a0 is the two point estimation of the lattice parameter

mode == range: lattice parameter is scanned in the specified range, as determined by the following two variables:

amin, amax -- range to scan the lattice parameter, from "amin" to "amax" [REQUIRED]

mode == stepwise: lattice parameter is scanned in stepwise fashion, starting at amin with increments da:

amin -- lower bound of the range to scan the lattice parameters [REQUIRED]
da -- increment (in Bohr units) for lattice parameter scan. This means that npoints SCF calculations will be performed at amin, amin+da, amin+2*da, ... [REQUIRED]

SUMMARY of the EOS namelist:

mode == auto:

    EOS {
           mode = auto
        npoints = integer-number (OPTIONAL)
             a0 = real-value     (OPTIONAL)
             B0 = small|medium|high|real-value (OPTIONAL)
            da0 = real-value     (OPTIONAL)
      scale_min = real-value     (OPTIONAL)
      scale_max = real-value     (OPTIONAL)
    }

mode == range:

    EOS {
           mode = range
        npoints = integer-number (OPTIONAL)
           amin = real-value     (REQUIRED)
           amax = real-value     (REQUIRED)
    }

mode == stepwise:

    EOS {
           mode = stepwise
        npoints = integer-number (OPTIONAL)
           amin = real-value     (REQUIRED)
             da = real-value     (REQUIRED)
    }

SOURCE

    ::pwtk::input::namelist EOS $content 
}

TABLE OF CONTENTS

::pwtk::eos::EOS