mod_strmat Module

Calculation of lattice sums for $l \leq 2l_{pot}$ $$\begin{equation} \sum_{rm} \frac{Y_{lm}\left(q(i)-q(j)-rm\right)}{\left| q(i)-q(j)-rm\right|^{l+1}} \end{equation}$$ in the case of $i = j$, $rm = 0$ is omitted. Rhe ewald method is used to perform the lattice summations the splitting parameter $\lambda$ is set equal $\frac{\sqrt(\pi)}{a_{lat}}$ ($a_{lat}$ is the lattice constant). If the contribution of the last shell of the direct and the reciprocal lattice is greater than 1.0e-8 a message is written