External Pressure

An external pressure may be applied to the unit cell by specifying a pressure tensor.

%BLOCK EXTERNAL_PRESSURE
[units]

$$\begin{array}{ccc} R_{xx} & R_{xy} & R_{xz} \\ & R_{yy} & R_{yz} \\ & & R_{zz} \\ \end{array}$$

%ENDBLOCK EXTERNAL_PRESSURE

[units] specifies the units in which the pressure is defined. If not present, the default is GPa.

Entry $R_{xx}$ is the $xx$-component of the pressure, $R_{xy}$ the $xy$-component etc.

The default is to apply no external pressure.