Computes variable = factor*tr(mat1).
TRACE,variable, mat1, mat2,[factor],[facnuc]
Computes variable = factor*trace(mat1 mat2) + facnuc*opnuc.
The result of the trace operation is stored in the MOLPRO variable variable, which can be used in subsequent operations.
If factor is not given, one is assumed. If facnuc is given, the nuclear contribution
multiplied by facnuc is added. It is assumed that either mat1 or mat2 has a nuclear contribution.
The default for facnuc is zero.