\(\renewcommand{\AA}{\text{Å}}\)

pair_style lambda/input/apip command

Syntax

pair_style lambda/input/apip cutoff

  • lambda/input/apip = style name of this pair style

  • cutoff = global cutoff (distance units)

pair_style lambda/input/csp/apip command

Syntax

pair_style lambda/input/csp/apip lattice keyword args

  • lambda/input/csp/apip = style name of this pair style

  • lattice = fcc or bcc or integer

    fcc = use 12 nearest neighbors to calculate the CSP like in a perfect fcc lattice
bcc = use 8 nearest neighbors to calculate the CSP like in a perfect bcc lattice
integer = use N nearest neighbors to calculate the CSP

  • zero or more keyword/args pairs may be appended

  • keyword = cutoff or N_buffer

    cutoff args = cutoff
  cutoff = distance in which neighboring atoms are considered (> 0)
N_buffer args = N_buffer
  N_buffer = number of additional neighbors, which are included in the j-j+N/2 calculation

Examples

pair_style lambda/input/csp/apip fcc
pair_style lambda/input/csp/apip fcc cutoff 5.0
pair_style lambda/input/csp/apip bcc cutoff 5.0 N_buffer 2
pair_style lambda/input/csp/apip 14

Description

This pair_styles calculates \(\lambda_i^\text{input}(t)\), which is required for fix lambda/apip.

The pair_style lambda_input sets \(\lambda_i^\text{input}(t) = 0\).

The pair_style lambda_input/csp calculates \(\lambda_i^\text{input}(t) = \text{CSP}_i(t)\). The centro-symmetry parameter (CSP) (Kelchner) is described in compute centro/atom.

The lattice argument is described in compute centro/atom and determines the number of neighboring atoms that are used to compute the CSP. The N_buffer argument allows to include more neighboring atoms in the calculation of the contributions from the pair j,j+N/2 to the CSP as discussed in (Immel).

The computation of \(\lambda_i^\text{input}(t)\) 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 potential 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 this pair_style. The switching parameter is calculated by fix lambda/apip, whereas the spatial transition zone of the switching parameter is calculated by pair_style lambda/zone/apip.

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.

Default

N_buffer=0, cutoff=5.0

(Kelchner) Kelchner, Plimpton, Hamilton, Phys Rev B, 58, 11085 (1998).

(Immel) Immel, Drautz and Sutmann, J Chem Phys, 162, 114119 (2025)