  We introduce the two-particle probability density $X(x)$ of
$x=\bm{r}_{12}\cdot\bm{p}_{12}=\left(\bm{r}_1-\bm{r}_2\right) \cdot
\left(\bm{p}_1-\bm{p}_2\right)$. We show how to derive $X(x)$, which we call
the Posmom intracule, from the many-particle wavefunction. We contrast it with
the Dot intracule [Y. A. Bernard, D. L. Crittenden, P. M. W. Gill, Phys. Chem.
Chem. Phys., 10, 3447 (2008)] which can be derived from the Wigner distribution
and show the relationships between the Posmom intracule and the one-particle
Posmom density [Y. A. Bernard, D. L. Crittenden, P. M. W .Gill, J.Phys. Chem.A,
114, 11984 (2010)]. To illustrate the usefulness of $X(x)$, we construct and
discuss it for a number of two-electron systems.
