pair_style pace command


pair_style pace ... keyword values ...
  • an optional keyword may be appended

  • keyword = product or recursive

    product = use product algorithm for basis functions
    recursive = use recursive algorithm for basis functions


pair_style pace
pair_style pace product
pair_coeff * * Cu-PBE-core-rep.ace Cu


Pair style pace computes interactions using the Atomic Cluster Expansion (ACE), which is a general expansion of the atomic energy in multi-body basis functions. (Drautz). The pace pair style provides an efficient implementation that is described in this paper (Lysogorskiy).

In ACE, the total energy is decomposed into a sum over atomic energies. The energy of atom i is expressed as a linear or non-linear function of one or more density functions. By projecting the density onto a local atomic base, the lowest order contributions to the energy can be expressed as a set of scalar polynomials in basis function contributions summed over neighbor atoms.

Only a single pair_coeff command is used with the pace style which specifies an ACE coefficient file followed by N additional arguments specifying the mapping of ACE elements to LAMMPS atom types, where N is the number of LAMMPS atom types:

  • ACE coefficient file

  • N element names = mapping of ACE elements to atom types

Only a single pair_coeff command is used with the pace style which specifies an ACE file that fully defines the potential. Note that unlike for other potentials, cutoffs are not set in the pair_style or pair_coeff command; they are specified in the ACE file.

The pair_style pace command may be followed by an optional keyword product or recursive, which determines which of two algorithms is used for the calculation of basis functions and derivatives. The default is recursive.

See the pair_coeff doc page for alternate ways to specify the path for the ACE coefficient file.

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 with user-specifiable parameters as described above. You never need to specify a pair_coeff command with I != J arguments for this style.

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

This pair style does not write its information to binary restart files, since it is stored in potential files. Thus, you need to re-specify the pair_style and pair_coeff commands in an input script that reads a restart file.

This pair style can only be used via the pair keyword of the run_style respa command. It does not support the inner, middle, outer keywords.


This pair style is part of the USER-PACE package. It is only enabled if LAMMPS was built with that package. See the Build package doc page for more info.



(Drautz) Drautz, Phys Rev B, 99, 014104 (2019).

(Lysogorskiy) Lysogorskiy, van der Oord, Bochkarev, Menon, Rinaldi, Hammerschmidt, Mrovec, Thompson, Csanyi, Ortner, Drautz, TBD (2021).