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## Option: stress

#### Syntax

`-stress <component> <σ>`

`-stress <file>`

#### Description

This option allows to deform the system elastically according to the given applied stress. The elastic tensor of the system must be defined before calling this option, e.g. with the option `-properties`.

The user has to provide the following information:

- component: stress component that will be affected, must be 'xx', 'yy', 'zz', 'yx', 'zx', 'zy', or 'p'.
- σ: value of the applied stress, in GPa. Use a positive value for tension, or a negative value for compression

If the stress component is "p" then an isostatic pressure is applied, and <σ> is actually be the value of the pressure. In other words the applied stress will be σxx = σyy = σzz = -<σ>, with all deviatoric stresses being zero.

Alternatively the stress components can be read from a <file>. The <file> must be a text file containing the keyword "Voigt" (without quotation marks) followed on the next line by the three first Voigt components of stress σxx, σyy, σzz, and on yet another line the last three components σyx, σzx, σzy. Alternatively the <file> can contain the keyword "stress" (without quotation marks) followed by the full 3x3 stress tensor (on three separate lines, three components per line).

From the given stress tensor, the system is deformed according to Hooke's law: εi = Cij σj .

In order to apply a deformation (strain) one can use the option `-deform`.

#### Default

By default no stress is applied to the system.

#### Examples

- `atomsk initial.cfg -stress xx 0.5 final.xyz`

  This will result in an error because the elastic tensor is not defined.

- `atomsk initial.cfg -prop Ctensor.txt -stress xx 0.5 final.xyz`

  This will read the elastic tensor from the file "Ctensor.txt", and apply a stress σxx = 0.5 GPa.

- `atomsk initial.cfg -prop Ctensor.txt -stress p 1.2 final.xyz`

  This will read the elastic tensor from the file "Ctensor.txt", and apply an isostatic pressure P = 1.2 GPa.

- `atomsk initial.cfg -prop Ctensor.txt -stress mystress.txt final.xyz`

  This will read the elastic tensor from the file "Ctensor.txt", and apply the stress tensor defined in "mystress.txt".

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