The self-consistent computation of electronic polarization in organic molecular crystals is extended to include, in first order, corrections in the continuous gas-phase charge distribution ρG(r). The potential ∆Φa(ra) at molecule a in the crystal is due to the difference between ρG(r) and a point-charge approximation. ∆Φa(ra), which represents atomic multipolar contributions, is evaluated for crystals of anthracene and perylenetetracarboxylic dianhydride (PTCDA). The corrections to the polarization energies of molecular cations are P+(1) = -0.25 and -0.14 eV for anthracene and PTCDA, respectively, while P-(1) = 0.25 and 0.18 eV for the anions. The leading term of atomic multipoles is the ∆Φa(ra)-charge interaction that corresponds to the charge-quadrupole term in the submolecular approach. There are also new contributions in ∆Φa(ra)-redistributed charge and coupling of induced dipoles to gradients of ∆Φa(ra). First-order correction to electronic polarization is a general approach that combines the advantages of discrete charges for self-consistent treatment of crystals with accurate electrostatic potentials based on the best available molecular charge distribution.
EPL (Europhysics Letters)
- Pub Date:
- December 2002
- Polymers and organic compounds;
- Dielectric properties of solids and liquids;
- Effects of atomic and molecular interactions on electronic structure