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# compute smd/tlsph/defgrad command

## Syntax

    compute ID group-ID smd/tlsph/defgrad

- ID, group-ID are documented in compute command

- smd/tlsph/defgrad = style name of this compute command

## Examples

    compute 1 all smd/tlsph/defgrad

## Description

Define a computation that calculates the deformation gradient. It is only meaningful for particles which interact according to the Total-Lagrangian SPH pair style.

See this PDF guide to use Smooth Mach Dynamics in LAMMPS.

## Output info

This compute outputs a per-particle vector of vectors (tensors), which can be accessed by any command that uses per-particle values from a compute as input. See the Howto output doc page for an overview of LAMMPS output options.

The per-particle vector values will be given dimensionless. See units. The per-particle vector has 10 entries. The first nine entries correspond to the xx, xy, xz, yx, yy, yz, zx, zy, zz components of the asymmetric deformation gradient tensor. The tenth entry is the determinant of the deformation gradient.

## Restrictions

This compute is part of the MACHDYN package. It is only enabled if LAMMPS was built with that package. See the Build package page for more info. TThis compute can only be used for particles which interact via the total Lagrangian SPH pair style.

## Related commands

smd/hourglass/error

## Default

none