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Spin-spin interaction

The subroutine SSC investigates the spin-spin operator, which has the tensorial form:

\begin{displaymath}H^{ss} \equiv \displaystyle {\sum_{ k }}
\left\{ H_{ss}^{(k+1 k-1 2, 1 1 2)} + H_{ss}^{(k-1 k+1 2, 1 1 2)} \right\},\end{displaymath}

and finds the submatrix element of this operator between functions with any number of open shells. This subroutine is used for all distributions except $\alpha\alpha\alpha\alpha$, $\alpha\beta\alpha\beta$, $\beta\alpha\beta\alpha$, $\alpha\beta\beta\alpha$, $\beta\alpha\alpha\beta$ and $\alpha\alpha\beta\beta$. In the latter cases, instead of subroutine SSC the subroutines SS1111, SS1212, SS1212, SS1221, SS1221 and SS1122 are used.

The subroutine SSA investigates the submatrix elements of the spin-spin interaction operator

\begin{displaymath}\left( n_i\lambda _in_j\lambda _j\vert\vert H_{ss}^{\left( k+...
...e }\lambda _i^{\prime }n_j^{\prime }\lambda _j^{\prime }\right)\end{displaymath}

and

\begin{displaymath}\left( n_i\lambda _in_j\lambda _j\vert\vert H_{ss}^{\left( k-...
...e }\lambda _i^{\prime }n_j^{\prime }\lambda _j^{\prime }\right)\end{displaymath}

respectively. This subroutine is used for all distributions except $\alpha\alpha\alpha\alpha$, $\alpha\beta\alpha\beta$, and $\beta\alpha\beta\alpha$. In the latter cases, instead of subroutine SSA the subroutine SS1 is used.



2001-12-07