Atomic multipolar contributions to electronic polarization in organic molecular crystals

Abstract

The self-consistent computation of electronic polarization inorganic molecular crystals is extended to include, in firstorder, corrections in the continuous gas-phase chargedistribution ρG(r). The potentialΔΦa(ra) at molecule a in the crystal is due tothe difference between ρG(r) and a point-chargeapproximation. ΔΦa(ra), which represents atomicmultipolar contributions, is evaluated for crystals of anthraceneand perylenetetracarboxylic dianhydride (PTCDA). The correctionsto the polarization energies of molecular cations areP+(1) = -0.25 and -0.14 eV for anthracene and PTCDA,respectively, while P−(1) = 0.25 and 0.18 eV for theanions. The leading term of atomic multipoles is theΔΦa(ra)-charge interaction that corresponds tothe charge-quadrupole term in the submolecular approach. Thereare also new contributions inΔΦa(ra)-redistributed charge and coupling ofinduced dipoles to gradients of ΔΦa(ra).First-order correction to electronic polarization is a generalapproach that combines the advantages of discrete charges forself-consistent treatment of crystals with accurate electrostaticpotentials based on the best available molecular chargedistribution.