Characterization of the B-Center Defect in Diamond through the Vibrational Spectrum: A Quantum-Mechanical Approach

Abstract

The B-center in diamond, which consists of a vacancy whose four first nearest-neighbors are nitrogen atoms, has been investigated at the quantum-mechanical level with an all-electron Gaussian-type basis set, hybrid functionals, and the periodic supercell approach. To simulate various defect concentrations, four cubic supercells have been considered, containing (before the creation of the vacancy) 64, 216, 512, and 1000 atoms, respectively. Whereas the B-center does not affect the Raman spectrum of diamond, several intense peaks appear in the IR spectrum, which should permit us to identify this defect. It turns out that of the seven peaks proposed by Sutherland in 1954, located at 328, 780, 1003, 1171, 1332, 1372, and 1426 cm, and frequently mentioned as fingerprints of the B center, the first one and the last three do not appear in the simulated spectrum at any concentration. The graphical animation of the modes confirms the attribution of the remaining three and also permits investigation of the nature of the full set of modes.

Interstitial nitrogen atoms in diamond. A quantum mechanical investigation of its electronic and vibrational properties

“…The prime motivation of this study, as on previous occasions, [25][26][27][28][29][30] is to show that all-electron quantum mechanical calculations based on the CRYSTAL code 37 can provide detailed, quantitative IR and Raman spectra for the common defects in diamond. The utility of this approach is predicated on the twin facts that perfect, or pristine diamond exhibits no IR features, for symmetry reasons, and that the Raman spectrum consists of a single, sharp one-phonon peak at 1332 cm −1 , which compares with the calculated B3LYP/6-21G value of 1317 cm −1 .…”

“…The utility of this approach is predicated on the twin facts that perfect, or pristine diamond exhibits no IR features, for symmetry reasons, and that the Raman spectrum consists of a single, sharp one-phonon peak at 1332 cm −1 , which compares with the calculated B3LYP/6-21G value of 1317 cm −1 . [25][26][27][28][29][30] It follows, therefore, that all IR features exhibited by real crystals, and all Raman features other than the sharp one-phonon peak, are due to the presence of defects. However, real crystals contain a multitude of defects, mostly of unknown provenance, so that the assignment of spectral features to individual defects is both difficult and uncertain.…”

“…Pople's standard 6-21G 52 all electron basis sets of Gaussian functions have been adopted for both carbon and nitrogen, except for values of 0.228 Bohr −2 and 0.30 Bohr −2 for the outermost sp orbitals of the host and dopant atoms respectively. As elsewhere, [25][26][27][28][29][30] the five parameters, Ti, that control the truncation of the infinite Coulomb and exchange series 37 were set to 10 −8 (T1-T4) and 10 −16 for T5, while the Self-Consistent Field (SCF) convergence threshold for the energy was set to 10 −10 hartree for vibration frequency calculations.…”

“…As in previous studies, [25][26][27][28][29][30] a periodic supercell approach has been used to simulate different defect concentrations. In this work two cubic supercells have been considered, containing respectively 64 + 1 (S64) and 216 + 1 (S216) atoms.…”

“…In this respect, given the specific spectroscopic fingerprint of different hybridizations of carbon atoms, 10,11 Infrared (IR) and Raman spectroscopies represent ideal experimental techniques with which to characterize the atomic nature of the various point-defects in both diamond and diamond-like materials. [12][13][14][15][16][17][18][19][20][21] In this regard, in a series of previous publications [25][26][27][28][29][30] some of the present authors have proposed the quantum-mechanical characterization of several point-defects in diamond, including the simulation of vibrational IR and Raman spectra.…”