We present a method to study the effects of isotopic composition on the Raman spectra of crystals, in which disorder is treated exactly without resorting to any kind of mean-field approximation. The Raman cross section is expressed in terms of a suitable diagonal element of the vibrational Green’s function, which is accurately and efficiently calculated using the recursion technique. This method can be used in conjunction with both semiempirical lattice-dynamical models and with first-principles interatomic force constants. We have applied our technique to diamond and germanium using the most accurate interatomic force constants presently available, obtained from density-functional perturbation theory. Our method correctly reproduces the light scattering in diamond—where isotopic effects dominates over the anharmonic ones—as well as in germanium, where anharmonic effects are larger.
Effects of isotopic disorder on the Raman spectra of crystals: theory and ab initio calculations for diamond and germanium / Vast, . N; Baroni, S.. - In: PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS. - ISSN 1098-0121. - 61:14(2000), pp. 9387-9392. [10.1103/PhysRevB.61.9387]
Effects of isotopic disorder on the Raman spectra of crystals: theory and ab initio calculations for diamond and germanium
Baroni, S.
2000-01-01
Abstract
We present a method to study the effects of isotopic composition on the Raman spectra of crystals, in which disorder is treated exactly without resorting to any kind of mean-field approximation. The Raman cross section is expressed in terms of a suitable diagonal element of the vibrational Green’s function, which is accurately and efficiently calculated using the recursion technique. This method can be used in conjunction with both semiempirical lattice-dynamical models and with first-principles interatomic force constants. We have applied our technique to diamond and germanium using the most accurate interatomic force constants presently available, obtained from density-functional perturbation theory. Our method correctly reproduces the light scattering in diamond—where isotopic effects dominates over the anharmonic ones—as well as in germanium, where anharmonic effects are larger.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.