Lattice distortion near vacancies in diamond and silicon. I

Abstract

Previous results (paper I), based on a dynamic relaxation procedure, coupled with a valence force potential function to represent the interaction between the atoms of the perfect crystal, have been used to calculate the distortion around point defects in a diamond-type crystal. The method has been applied to the isolated neutral vacancy in diamond and silicon for two alternative choices of rebonding forces for the vacancy electrons. In one case the electronic forces have been estimated from a detailed molecular orbital calculation, while in an alternative approach a generalized Morse-type potential relationship has been used. The formation energy of the neutral vacancy has also been calculated. For the vacancy in diamond values of 0.35 and 6.47 eV have been obtained using two alternative approximations to calculate the molecular orbital force terms, while with the Morse potential a value of-0.37 eV is obtained. The vacancy in silicon is estimated to have a formation energy of-38.8 eV using the molecular orbital parameters and-16.35 eV using the alternative method. The volume changes associated with the diamond-type system containing a vacancy are also calculated. The results suggest that one of the approximations used is not valid. Some of the possibilities are discussed.

Theoretical implications of the stress and magnetic field splitting of the GR1 line in diamond

“…Accordingly, not only is the observed g value associated with a delocalised magnetic moment, but also the Zeeinan operator in the IT, state is quenched because of the dynamic Jahn-Teller interaction. The magnitude of this Jahn-Teller quenching can be evaluated from the reported stress splitting of the GR1 transitions or from theoretical studies of the elastic properties of the centre (Larkins and Stoneham 1971). In this paper we calculate the g value of IT2, and show the result compares very favourably with the value reported by Douglas and Runciman(1977).…”

Strongly inhomogeneous distribution of spectral properties of silicon-vacancy color centers in nanodiamonds

“…About 70 % of the group V photoluminescence spectra with one distinct sideband peak display a shift of the sideband peak from the ZPL between 37 meV to 43 meV. The range of line shifts for the prominent sideband peak coincides with a well-known feature at 42 meV, associated with SiV centers [55,58], but also to a larger number of optically active defects [55]. The occurrence of this 42 meV sideband feature for a large number of defects and the absence of isotopic variations [36], favors an assignment as non-localized lattice vibration.…”

Electronic structure of the V-centre in MgO

“…In principle, these local corrections can be calculated directly by calculating energies in a compressed crystal, for example. This works well for silicon and diamond (Larkins and Stoneham 1971), but there are technical problems because of the long-range forces in ionic crystals, and comparable calculations would be too demanding here.…”