Difference between revisions of "Pressure"

Pressure ($p$) is the force per unit area applied on a surface, in a direction perpendicular to that surface, i.e. the scalar part of the stress tensor. In thermodynamics the pressure is given by
$p = - \left.\frac{\partial A}{\partial V} \right\vert_{T,N} = k_BT \left.\frac{\partial \ln Q}{\partial V} \right\vert_{T,N}$
where $A$ is the Helmholtz energy function, $V$ is the volume, $k_B$ is the Boltzmann constant, $T$ is the temperature and $Q (N,V,T)$ is the canonical ensemble partition function.