# compute stress/cartesian command

## Syntax

``` LAMMPS
compute ID group-ID stress/cartesian args
```

-   ID, group-ID are documented in [compute](compute) command
-   args = argument specific to the compute style

<!-- -->

    *stress/cartesian* args = dim1 bin_width1 dim2 bin_width2 keyword
      dim1 = *x* or *y* or *z*
      bin_width1 = width of the bin
      dim2 = *x* or *y* or *z* or *NULL*
      bin_width2 = width of the bin
      keyword = *ke* or *pair* or *bond*

## Examples

``` LAMMPS
compute 1 all stress/cartesian x 0.1 NULL 0
compute 1 all stress/cartesian y 0.1 z 0.1
compute 1 all stress/cartesian x 0.1 NULL 0 ke pair
```

## Description

Compute *stress/cartesian* defines computations that calculate profiles
of the diagonal components of the local stress tensor over one or two
Cartesian dimensions, as described in
[(Ikeshoji)\<Ikeshoji2\>]{.title-ref}. The stress tensor is split into a
kinetic contribution $P^k$ and a virial contribution $P^v$. The sum
gives the total stress tensor $P = P^k+P^v$. This compute obeys momentum
balance through fluid interfaces. They use the Irving\--Kirkwood
contour, which is the straight line between particle pairs.

::: versionadded
15Jun2023

Added support for bond styles
:::

This compute only supports pair and bond (no angle, dihedral, improper,
or kspace) forces. By default, if no extra keywords are specified, all
supported contributions to the stress are included (ke, pair, bond). If
any keywords are specified, then only those components are summed.

## Output info

The output columns for *stress/cartesian* are the position of the center
of the local volume in the first and second dimensions, number density,
$P^k_{xx}$, $P^k_{yy}$, $P^k_{zz}$, $P^v_{xx}$, $P^v_{yy}$, and
$P^v_{zz}$. There are 8 columns when one dimension is specified and 9
columns when two dimensions are specified. The number of bins (rows) is
$(L_1/b_1)(L_2/b_2)$, where $L_1$ and $L_2$ are the lengths of the
simulation box in the specified dimensions and $b_1$ and $b_2$ are the
specified bin widths. When only one dimension is specified, the number
of bins (rows) is $L_1/b_1$.

This array can be output with [fix ave/time](fix_ave_time),

``` LAMMPS
compute p all stress/cartesian x 0.1
fix 2 all ave/time 100 1 100 c_p[*] file dump_p.out mode vector
```

The values calculated by this compute are \"intensive\". The stress
values will be in pressure [units](units). The number density values are
in inverse volume [units](units).

NOTE 1: The local stress does not include any Lennard-Jones tail
corrections to the stress added by the [pair_modify tail
yes](pair_modify) command, since those are contributions to the global
system pressure.

NOTE 2: The local stress profiles generated by these computes are
similar to those obtained by the [method-of-planes
(MOP)](compute_stress_mop). A key difference is that compute
[stress/mop/profile](compute_stress_mop) considers particles crossing a
set of planes, while *stress/cartesian* computes averages for a set of
small volumes. Moreover, this compute computes the diagonal components
of the stress tensor $P_{xx}$, $P_{yy}$, and $P_{zz}$, while
*stress/mop/profile* computes the components $P_{ix}$, $P_{iy}$, and
$P_{iz}$, where $i$ is the direction normal to the plane.

More information on the similarities and differences can be found in
[(Ikeshoji)\<Ikeshoji2\>]{.title-ref}.

## Restrictions

These computes calculate the stress tensor contributions for pair and
bond forces only (no angle, dihedral, improper, or kspace force). It
requires pairwise force calculations not available for most many-body
pair styles.

These computes are part of the EXTRA-COMPUTE package. They are only
enabled if LAMMPS was built with that package. See the [Build
package](Build_package) doc page for more info.

## Related commands

[compute stress/atom](compute_stress_atom), [compute
pressure](compute_pressure), [compute
stress/mop/profile](compute_stress_mop), [compute
stress/spherical](compute_stress_curvilinear), [compute
stress/cylinder](compute_stress_curvilinear)

------------------------------------------------------------------------

::: {#Ikeshoji2}
**(Ikeshoji)** Ikeshoji, Hafskjold, Furuholt, Mol Sim, 29, 101-109,
(2003).
:::