\(\renewcommand{\AA}{\text{Å}}\)

pair_style eam/apip command

Constant precision variant: eam

pair_style eam/fs/apip command

Constant precision variant: eam/fs

Syntax

pair_style eam/apip
pair_style eam/fs/apip

Examples

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

Description

Style eam computes pairwise interactions for metals and metal alloys using embedded-atom method (EAM) potentials (Daw). The total energy \(E_i\) of an atom \(i\) is given by

\[E_i^\text{EAM} = F_\alpha \left(\sum_{j \neq i}\ \rho_\beta (r_{ij})\right) + \frac{1}{2} \sum_{j \neq i} \phi_{\alpha\beta} (r_{ij})\]

where \(F\) is the embedding energy which is a function of the atomic electron density \(\rho\), \(\phi\) is a pair potential interaction, and \(\alpha\) and \(\beta\) are the element types of atoms \(i\) and \(j\). The multi-body nature of the EAM potential is a result of the embedding energy term. Both summations in the formula are over all neighbors \(j\) of atom \(i\) within the cutoff distance. EAM is documented in detail in pair_style eam.

The potential energy \(E_i\) of an atom \(i\) of an adaptive-precision interatomic potential (APIP) according to (Immel) is given by

\[E_i^\text{APIP} = \lambda_i E_i^\text{(fast)} + (1-\lambda_i) E_i^\text{(precise)}\,,\]

whereas the switching parameter \(\lambda_i\) is computed dynamically during a simulation by fix lambda/apip or set prior to a simulation via set.

The pair style eam/fs/apip computes the potential energy \(\lambda_i E_i^\text{EAM}\) and the corresponding force and should be combined with a precise potential like pair_style pace/precise/apip that computes the potential energy \((1-\lambda_i) E_i^\text{(precise)}\) and the corresponding force via pair_style hybrid/overlay.

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

For atom type pairs I,J and I != J, where types I and J correspond to two different element types, mixing is performed by LAMMPS as described above with the individual styles. You never need to specify a pair_coeff command with I != J arguments for the eam/apip styles.

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

The eam/apip pair styles do not write their information to binary restart files, since it is stored in tabulated potential files. Thus, you need to re-specify the pair_style and pair_coeff commands in an input script that reads a restart file.

The eam/apip pair styles can only be used via the pair keyword of the run_style respa command. They do not support the inner, middle, outer keywords.

Restrictions

This pair styles are 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

none

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

(Daw) Daw, Baskes, Phys Rev Lett, 50, 1285 (1983). Daw, Baskes, Phys Rev B, 29, 6443 (1984).