First-Principles Calculation of the Electric Field Gradient of ${\mathrm{Li}}_3$N

The electric field gradient can be obtained from self-consistent energy-band calculations by the linearized-augmented-plane-wave method provided that a general potential is used. This first-principles method, which does not rely on any Sternheimer antishielding factor, is tested for ${\mathrm{Li}}_3$N and yields electric field gradients for Li(1), Li(2), and N in excellent agreement with NMR experiments. The electric field gradient is mainly determined by local distortions of the electronic charge density, especially in the case of the polarizable ${\mathrm{N}}^{3-}$ ion.