<tt>PSTRESS</tt> (in unit of eV) is a Rank 2 tensor (mass times velocity times velocity),
which is an intermediate result for computing the total Virial stress
<tt>TSTRESS</tt> (in unit of eV/&Aring;<sup>3</sup>).

<p>
<tt>TSTRESS = (VIRIAL + PSTRESS) / OMEGA</tt>

<p>
Also see <tt>VIRIAL</tt>, <tt>TSTRESS</tt>, <tt>TSTRESSinMPa</tt>.
