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# pair_style lambda/zone/apip command

## Syntax

    pair_style lambda/zone/apip cutoff

- lambda/zone/apip = style name of this pair style

- cutoff = global cutoff (distance units)

## Examples

    pair_style lambda/zone/apip 12.0

## Description

This pair_style calculates \(\lambda_{\text{min},i}\), which is required for fix lambda/apip. The meaning of \(\lambda_{\text{min},i}\) is documented in fix lambda/apip, as this pair_style is for use with fix lambda/apip only.

This pair_style requires only the global cutoff as argument. The remaining quantities, that are required to calculate \(\lambda_{\text{min},i}\) are extracted from fix lambda/apip and, thus, do not need to be passed to this pair_style as arguments.

Warning

The cutoff given as argument to this pair style is only relevant for the neighbor list creation. The radii, which define \(r_{\lambda,\text{hi}}\) and \(r_{\lambda,\text{lo}}\) are defined by fix lambda/apip.

The computation of \(\lambda_{\text{min},i}\) is done by this pair_style instead of by fix lambda/apip, as this computation takes time and this pair_style can be included in the load-balancing via fix atom_weight/apip.

A code example for the calculation of the switching parameter for an adaptive-precision interatomic potential (APIP) is given in the following: The adaptive-precision potential is created by combining pair_style eam/fs/apip and pair_style pace/precise/apip. The input, from which the switching parameter is calculated, is provided by pair lambda/input/csp/apip. The switching parameter is calculated by fix lambda/apip, whereas the spatial transition zone of the switching parameter is calculated by this pair style.

    pair_style hybrid/overlay eam/fs/apip pace/precise/apip lambda/input/csp/apip fcc cutoff 5.0 lambda/zone/apip 12.0
    pair_coeff * * eam/fs/apip Cu.eam.fs Cu
    pair_coeff * * pace/precise/apip Cu_precise.yace Cu
    pair_coeff * * lambda/input/csp/apip
    pair_coeff * * lambda/zone/apip
    fix 2 all lambda/apip 3.0 3.5 time_averaged_zone 4.0 12.0 110 110 min_delta_lambda 0.01

## Mixing, shift, table, tail correction, restart, rRESPA info

The cutoff distance for this pair style can be mixed. The default mix value is geometric. See the “pair_modify” command for details.

This pair style does not support the pair_modify shift, table, and tail options.

This pair style writes no information to binary restart files, so pair_style and pair_coeff commands need to be specified in an input script that reads a restart file.

This pair style does not support the use of the inner, middle, and outer keywords of the run_style respa command.

## Restrictions

This fix is part of the APIP package. It is only enabled if LAMMPS was built with that package. See the Build package page for more info.

## Related commands

fix lambda/apip, fix atom_weight/apip pair_style lambda/input/apip, pair_style eam/apip, pair_style pace/apip, fix lambda_thermostat/apip,

## Default

none