This property is the interaction between the nuclear quadrupole moment of a nucleus 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 calculated as an 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 DALTON INPUT
It is noteworthy that due to it's dependence on the electronic environment close to the nucleus of interest, it puts strict demands on the basis set, similar to that needed for spin-spin coupling constants (Sec. 10.5). Electron correlation may also be of importance, see for instance Ref. [47].