Electric field gradients are highly pair-additive

The electric field gradients at the central deuterons in one hundred cluste rs consisting of heavy water molecules, previously calculated in a supermol ecular approach including many-body effects, is calculated assuming pair-ad ditivity. Excellent pair-additivity of the electric field gradient is found for the water clusters. This result is confirmed for one hundred clusters extracted from a water-DMSO mixture. The use of pair-additivity results in substantial computer time savings in the quantum chemical calculation of th e electric field gradients for nuclei in liquid systems using the so-called cluster approach, and hence their quadrupole coupling constants. It also p ermits the simulation of quadrupolar relaxation times from electric field g radient hypersurfaces obtained within the pair-additive approximation. (C) 2001 Elsevier Science B.V. All rights reserved.