20.2 Electric Field Gradient

The electric field gradient and the nuclear quadrupole interaction can be calculated with the keywords $efg and $nqi in the proper section of the respective module. In relativistic calculations, the picture-change correction should be included. Please see Sec. 18.3 of the EPR chapter for further details. The nuclear spin and other constants such as the nuclear quadrupole moment can be set in the atoms data group of the control file. This data group may, for instance, look like

$atoms
    basis =dyall-vdz
hg 1
    ncisotope=  your-isotope
    nucquad=    your-quadrupole-moment
    nucspin=    your-spin