Tabulated EAM¶

Description¶

The tabeam_force operator computes a single-species EAM potential whose three functions are given as tables. The pair term \(\phi(r)\), the electron density \(\rho(r)\) and the embedding function \(F(\rho)\), together with their derivatives, are interpolated with cubic splines:

\[ \phi(r) = \mathcal{S}_{\phi}(r), \qquad \rho(r) = \mathcal{S}_{\rho}(r), \qquad F(\rho) = \mathcal{S}_{F}(\rho) \]

The values and the derivatives are interpolated independently, so the tables must provide consistent derivatives.

See the EAM overview for the total energy and the available operators (tabeam_force, tabeam_emb, tabeam_force_reuse_emb, tabeam_init). For multi-species tabulated potentials in the standard setfl format, use EAM alloy.

The tables are read from a YAML file (searched in the data paths) with the following keys:

Key	Grid	Description
`r`	—	Distance grid
`phi`, `dphi`	`r`	Pair term and its derivative
`rho`, `drho`	`r`	Electron density and its derivative
`rhof`	—	Electron density grid of the embedding function
`f`, `df`	`rhof`	Embedding function and its derivative
`format`	—	Optional. `exastampv1`: values are plain numbers in SI units (m, J, N)

Without format, each value is read as a quantity, so units can be given value by value.

YAML syntax¶

tabeam_force:
  rcut: VALUE UNITS
  parameters: FILENAME

VALUE = Physical value of the intended parameter.
UNITS = Units of the provided value that will be passed to the conversion helper for internal units conversion.
FILENAME = YAML file with the tables. parameters: { file: FILENAME } is also accepted, and so are the tables given directly under parameters.

Usage example¶

Copper (tabulated Sutton–Chen)

tabeam_force:
  rcut: 7.29 ang
  parameters: tab_sc.yaml

compute_force: tabeam_force

tab_sc.yaml is shipped in exaStamp/data/potentials/. The complete input is exaStamp/data/regression_new/potentials/eam/eam_tab/single_specy.msp. This potential runs on CPU only.