Estimates of van der Waals coefficients in isoelectronic alkali halide crystals from optical data

Abstract

Abstract The coefficients (c vdW) for the dipole-dipole van der Waals interactions between two ions in the isoelectronic alkali halide crystals are estimated within Mayer's method from the optical spectra. The Kramers-Kronig analyses of the recent optical and reflection measurements, obtained mainly by the extensive use of synchrotron radiation, lead to the determination of the optical constants and hence to the “experimental” values of the matrix elements of the dipole moment operator between the ground and the excited electronic states. These matrix elements appear in the expression of the c vdW coefficients from second order perturbation theory in the asymptotic expansion. The adopted procedure is applied to the rare gas crystals for the first time. The reported values of the electronic polarizabilities and the c vdW of Kr indicate the expected agreement with the corresponding gas phase values. The effect of the full local field corrections, appropriate for these insulators, on the c vdW coefficients i...