First principles study of structural, electronic and vibrational properties of heavily boron-doped diamond

The structural, electronic and vibrational properties of a series of heavily B-doped diamond models have been investigated using the density functional theory within a local density approximation. The doped models C_{64 - n}B_n (n = 1 - 3) were constructed using supercell techniques. The structural and electronic calculations confirmed that the B dimers are always energetically stable and electrical inactive. The superconducting transition temperature T_C is not only decided by the B concentration, but also by the lattice configurations of boron atoms. The vibrational frequencies and eigenmodes were determined using the linear response approach, while Raman intensities were obtained by the second response method. The Raman analysis in terms of atomic vibrations found that the "500 cm^-1" and "1230 cm^-1" bands are both superposed bands including not only C vibrations but also B-B vibrations and B-C vibrations, respectively. The calculated Raman spectra with isotopic substitutions are in excellent agreement with corresponding experimental results. The reasonable explanation was provided for no obvious Raman shift of main bands from ¹⁰B¹²C to ¹¹B¹²C model.