Next: Option moments
trace will calculate the trace of density times overlap matrix:
If the orbitals are orthonormal, should yield the total number of
electrons in your molecule. If this is not true, your MO-vector will
most probably be erroneous. For example, the vector might belong to
another geometry or basis set. As this is a very sensitive test for
errors like these and the calculation requires almost no time, you
should always switch on this option.