This property is the interaction between the nuclear quadrupole moment of a nuclei with spin greater or equal to 1, and the electric field gradient generated by the movement of the electron cloud around the nucleus. Quantum mechanically it is a simple expectation value of the electric field gradient at the nucleus, and it is obtained by the input:
**DALTON INPUT .RUN PROPERTIES **WAVE FUNCTIONS .HF **PROPERTIES .NQCC *END OF INPUT
It is noteworthy that due to it's dependence on the immediate
electronic environment around the nucleus of interest, it puts severe
demands on the basis set, similar to those needed for spin-spin
coupling
constants (Sec. 
). Correlation may also be of
importance, see for instance Ref. [27].