# compute stress/cylinder command

# compute stress/spherical command

## Syntax

``` LAMMPS
compute ID group-ID style args
```

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

<!-- -->

    *stress/cylinder* args = zlo zh Rmax bin_width keyword
      zlo = minimum z-boundary for cylinder
      zhi = maximum z-boundary for cylinder
      Rmax = maximum radius to perform calculation to
      bin_width = width of radial bins to use for calculation
      keyword = ke (zero or one can be specified)
        ke = yes or no
    *stress/spherical*
      x0, y0, z0 = origin of the spherical coordinate system
      bin_width = width of spherical shells
      Rmax = maximum radius of spherical shells

## Examples

``` LAMMPS
compute 1 all stress/cylinder -10.0 10.0 15.0 0.25
compute 1 all stress/cylinder -10.0 10.0 15.0 0.25 ke no
compute 1 all stress/spherical 0 0 0 0.1 10
```

## Description

Compute *stress/cylinder*, and compute *stress/spherical* define
computations that calculate profiles of the diagonal components of the
local stress tensor in the specified coordinate system. The stress
tensor is split into a kinetic contribution $P^k$ and a virial
contribution $P^v$. The sum gives the total stress tensor $P = P^k+P^v$.
These computes can for example be used to calculate the diagonal
components of the local stress tensor of surfaces with cylindrical or
spherical symmetry. These computes obeys momentum balance through fluid
interfaces. They use the Irving\--Kirkwood contour, which is the
straight line between particle pairs.

The compute *stress/cylinder* computes the stress profile along the
radial direction in cylindrical coordinates, as described in
[(Addington)\<Addington1\>]{.title-ref}. The compute *stress/spherical*
computes the stress profile along the radial direction in spherical
coordinates, as described in [(Ikeshoji)\<Ikeshoji4\>]{.title-ref}.

## Output info

The default output columns for *stress/cylinder* are the radius to the
center of the cylindrical shell, number density, $P^k_{rr}$,
$P^k_{\phi\phi}$, $P^k_{zz}$, $P^v_{rr}$, $P^v_{\phi\phi}$, and
$P^v_{zz}$. When the keyword *ke* is set to *no*, the kinetic
contributions are not calculated, and consequently there are only 5
columns: the position of the center of the cylindrical shell, the number
density, $P^v_{rr}$, $P^v_{\phi\phi}$, and $P^v_{zz}$. The number of
bins (rows) is $R_\text{max}/b$, where $b$ is the specified bin width.

The output columns for *stress/spherical* are the position of the center
of the spherical shell, the number density, $P^k_{rr}$,
$P^k_{\theta\theta}$, $P^k_{\phi\phi}$, $P^v_{rr}$,
$P^v_{\theta\theta}$, and $P^v_{\phi\phi}$. There are 8 columns and the
number of bins (rows) is $R_\text{max}/b$, where $b$ is the specified
bin width.

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

``` LAMMPS
compute 1 all stress/spherical 0 0 0 0.1 10
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.

## Restrictions

These computes calculate the stress tensor contributions for pair styles
only (i.e., no bond, angle, dihedral, etc. contributions, and in the
presence of bonded interactions, the result may be incorrect due to
exclusions for [special bonds](special_bonds) excluding pairs of atoms
completely). It requires pairwise force calculations not available for
most many-body pair styles. Note that $k$-space calculations are also
excluded.

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/cartesian](compute_stress_cartesian)

## Default

The keyword default for ke in style *stress/cylinder* is yes.

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

::: {#Ikeshoji4}
**(Ikeshoji)** Ikeshoji, Hafskjold, Furuholt, Mol Sim, 29, 101-109,
(2003).
:::

::: {#Addington1}
**(Addington)** Addington, Long, Gubbins, J Chem Phys, 149, 084109
(2018).
:::