Self-diffusion parameters in carbon-subgroup crystals

Self-diffusion parameters have been calculated for crystals of the carbon subgroup C (diamond), Si, Ge, α-Sn, Pb. It is shown that consideration of quantum effects in the delocalization of atoms leads to the following effect: at low temperatures (below the Debye temperature), the self-diffusion parameters depend strongly on temperature and the self-diffusion entropy is negative: sd < 0. With an increase in temperature, the function sd takes positive values. All thermodynamic parameters of self-diffusion in semiconductor crystals of carbon subgroup were calculated without any fitting parameters. The temperature dependences of self-diffusion parameters were studied for IVa-subgroup crystals upon isobaric heating from T = 0 K to the melting point. A good agreement with both experimental data and theoretical estimates obtained by other researchers is obtained. The correlation between the entropy and enthalpy of self-diffusion, as well as the correlation between the volume and entropy of self-diffusion for the entire temperature range under consideration, are discussed.