# pair_style sph/rhosum command

## Syntax

pair_style sph/rhosum Nstep

• Nstep = timestep interval

## Examples

pair_style sph/rhosum 10
pair_coeff * * 2.4


## Description

The sph/rhosum style computes the local particle mass density rho for SPH particles by kernel function interpolation, every Nstep timesteps.

See this PDF guide to using SPH in LAMMPS.

The following coefficients must be defined for each pair of atoms types via the pair_coeff command as in the examples above.

• h (distance units)

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

This style does not support mixing. Thus, coefficients for all I,J pairs must be specified explicitly.

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

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

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

## Restrictions

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