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The rapid solidification of Ti3Al was studied with the constant-pressure and constant-temperature molecular dynamics (NPT-MD) technique to obtain an atomistic description of glass formation and crystallization in the alloy. The embedded atom method (EAM) potential for the Ti–Al binary system recently developed by Zope and Mishin (2003 Phys. Rev. B 68 024102) was applied in the simulations. The effects of different cooling rates on the glass formation and crystallization of liquid Ti3Al were studied. In addition, the crystallization of the amorphous Ti3Al as a function of increasing temperature was also studied. The calculated internal energy change and radial distribution function during cooling and heating processes provided a good picture of the structural transformations, and the results were consistent with the results obtained experimentally.

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A first-principle plane-wave pseudopotential method based on the density function theory (DFT) was employed to investigate the effects of vacancy cluster (VC) defects on the band structure and thermoelectric properties of silicon (Si) crystals. Simulation results showed that various VC defects changed the energy band and localized electron density distribution of Si crystals and caused the band gap to decrease with increasing VC size. The results can be ascribed to the formation of a defect level produced by the dangling bonds, floating bonds, or high-strain atoms surrounding the VC defects. The appearance of imaginary frequencies in the phonon spectrum of defective Si crystals indicates that the defect-region structure is dynamically unstable and demonstrates phase changes. The phonon dispersion relation and phonon density of state were also investigated using density functional perturbation theory. The obtained Debye temperature (θ D) for a perfect Si crystal had a minimum value of 448 K at T = 42 K and a maximum value of 671 K at the high-temperature limit, which is consistent with the experimental results reported by Flubacher. Moreover, the Debye temperature decreased with increases in the VC size. VC defects had minimal effects on the heat capacity (C v) value when temperatures were below 150 K. As the temperature was higher than 150 K, the heat capacity gradually increased with increasing temperature until it achieved a constant value of 11.8 cal/cell·K. The heat capacity significantly decreased as the VC size increased. For a 2 × 2 × 2 superlattice Si crystal containing a hexagonal ring VC (HRVC10), the heat capacity decreased by approximately 17%.