Xiang-Dong Yang

High-pressure structure and elastic properties of tantalum single crystal: First principles investigation

Since knowledge of the structure and elastic properties of Ta at high pressures is critical for addressing the recent controversies regarding the high-pressure stable phase and elastic properties, we perform a systematical study on the high-pressure structure and elastic properties of the cubic Ta by using the first-principles method. Results show that the initial body-centered cubic phase of Ta remains stable even up to 500 GPa and the high-pressure elastic properties are excellently consistent with the available experimental results. Besides, the high-pressure sound velocities of the single- and poly-crystals Ta are also calculated based on the elastic constants, and the predications exhibit good agreement with the existing experimental data.

Correlation Between Energy Transfer Rate and Atomization Energy of Some Trinitro Aromatic Explosive Molecules

An assumptive theoretical relationship is suggested to describe the property of molecular atomization energy and energy transfer rate in the initiation of explosions. To investigate the relationship between atomization energy and energy transfer rate, the number of doorway modes of explosives is estimated by the theory of Dlott and Fayer in which the rate is proportional to the number of normal mode vibrations. It was evaluated frequencies of normal mode vibrations of eight molecules by means of density functional theory (DFT) at the b3p86/6-31G(d,p) level. It is found that the number of doorway modes shows a linear correlation to the atomization energies of the molecules, which were also calculated by means of the same method. A mechanism of this correlation is discussed. It is also noted that in those explosives with similar molecular structure and molecular weight, the correlation between the atomization energy and the number of doorway modes is higher.

Spectroscopic investigations on NO+(X1Σ+, a3Σ+, A1Π) ion using multi-reference configuration interaction method and correlation-consistent sextuple basis set augmented with diffuse functions

Three low-lying electronic states (X1Σ+, a3Σ+, and A1Π) of NO+ ion are studied using the complete active space self-consistent-field (CASSCF) method followed by highly accurate valence internally contracted multi-reference configuration interaction (MRCI) approach in combination of the correlation-consistent sextuple basis set augmented with diffuse functions, aug-cc-pV6Z. The potential energy curves (PECs) of the NO+(X1Σ+, a3Σ+, A1Π) are calculated. Based on the PECs, the spectroscopic parameters Re, De, ωe, ωeχe, αe, Be, and D0 are reproduced, which are in excellent agreement with the available measurements. By numerically solving the radial Schrodinger equation of nuclear motion using the Numerov method, the first 20 vibrational levels, inertial rotation and centrifugal distortion constants of NO+(X1Σ+, a3Σ+, A1Π) ion are derived when the rotational quantum number J is equal to zero (J = 0) for the first time, which accord well with the available measurements. Finally, the analytical potential energy functions of these states are fitted, which are used to accurately derive the first 20 classical turning points when J = 0. These results are compared in detail with those of previous investigations reported in the literature.