[en] The splitting of potential energy levels for ground state X²Π_g of O^x₂ (x = +1, −1) under spin—orbit coupling (SOC) has been calculated by using the spin-orbit (SO) multi-configuration quasi-degenerate perturbation theory (SO-MCQDPT). Their Murrell–Sorbie (M–S) potential functions are gained, and then the spectroscopic constants for electronic states ²Π_1/2 and ²Π_3/2 are derived from the M–S function. The vertical excitation energies for O^x₂ (x = +1, −1) are v[O⁺¹₂ (²Π_3/2 → X²Π_1/2)] = 195.652cm⁻¹, and v[O⁻¹₂(²Π_1/2 → X²Π_3/2)] = 182.568cm⁻¹, respectively. All the spectroscopic data for electronic states ²Π_1/2 and ²Π_3/2 are given for the first time

[en] The total internal partition sums were calculated in the product approximation at temperatures up to 5000 K for the asymptotic asymmetric-top HO₂ molecule. The calculations of the rotational partition function and the vibrational partition function were carried out with the rigid-top model and in the harmonic oscillator approximation, respectively. Our values of the total internal partition sums are consistent with the data of HITRAN database with -0.14% at 296 K. Using the calculated partition functions, we have calculated the line intensities of v₂ band of HO₂ at several high temperatures. The results showed that the calculated line intensities are in very good agreement with those of HITRAN database at temperatures up to 3000 K, which provides a strong support for the calculations of partition functions and line intensities at high temperatures. Then we have extended the calculation to higher temperatures. The simulated spectra of v₂ band of the asymptotic asymmetric-top HO₂ molecule at 4000 and 5000K are also obtained

[en] The total internal partition sums (TIPS) are calculated at the temperature up to 6000 K for ¹²C¹⁶O₂. Using the calculated partition functions, we produce the line intensities of ν₃ band of ¹²C¹⁶O₂ at several high temperatures. The results show that the calculated line intensities are in very good agreement with those of HITRAN database at the temperature up to 3000 K, which provides a strong support for the calculations of TIPS and line intensities at high temperature. Then the calculation is extended to further high temperature, and the simulated spectra of ν₃ band of ¹²C¹⁶O₂ at 5000 and 6000 K are reported.

[en] First-principles study of structural, elastic, and electronic properties of the B20 structure OsSi has been reported using the plane-wave pseudopotential density functional theory method. The calculated equilibrium lattice and elastic constants are in good agreement with the experimental data and other theoretical results. The dependence of the elastic constants, the aggregate elastic modulus, the deviation from the Cauchy relation, the elastic wave velocities in different directions and the elastic anisotropy on pressure have been obtained and discussed. This could be the first quantitative theoretical prediction of the elastic properties under high pressure of OsSi compound. Moreover, the electronic structure calculations show that OsSi is a degenerate semiconductor with the gap value of 0.68 eV, which is higher than the experimental value of 0.26 eV. The analysis of the PDOS reveals that hybridization between Os d and Si p states indicates a certain covalency of the Os-Si bonds. (condensed matter: structural, mechanical, and thermal properties)

[en] The line intensities of 0010-0000 transition of the symmetric-top PH₃ molecule at several temperature were calculated by directly calculating the partition functions and regarding the rotationless transition dipole moment squared as a constant. The calculated values of the total internal partition sums (TIPS) are consistent with the data of HITRAN database with -0.075% at 296 K. The calculated line intensities data at 1000 K and 3000 K are also in excellent agreement with the data in HITRAN database, which provide a strong support for the calculations of partition function and line intensity at high temperature. Then we extended the calculation to higher temperature. The line intensities and simulated spectra of υ₃ band of the symmetric-top PH₃ molecule at 4000 and 5000 K were reported. The results are of significance for the studying of the molecular high-temperature spectrum including experimental measurements and theoretical calculation. (authors)

[en] In this paper, the ab initio quantum mechanics method is used for a further investigation of the interactional potential energy functions of He atom and O₂. By means of different methods and basis sets, the energy data in the space have been calculated. Finally the accurate He-02 interactional potential energy functions are obtained by using QCISD(T)/6-311 + + G (3df, 2pd) with Boy and Bernardi's Full Couterpoise to eliminate the basis set superposition error (BSSE). The calculated differential cross sections of He-O₂ collision are in good agreement with the experiment data. The rule of differential cross sections of He-O₂ collision at different collision energies has been derived. (authors)

[en] The line intensities of 001-000 transition of the asymptotic asymmetric-top O₃ molecule at several temperatures are calculated by directly calculating the partition functions and regarding the rotationless transition dipole moment squared as a constant. The calculated values of the total internal partition sums (TIPS) are consistent with the data of HITRAN database with -0.61% at 296 K. The calculated line intensity data at 500 K and 3000 K are also in excellent agreement with the data in HITRAN database with less than 0.659% and 5.458% at 500 K and 3000 K, which provide a strong support for the calculations of partition function and line intensity at high temperature. Then we extend the calculation to higher temperatures. The line intensities and simulated spectra of ν₃ band of the asymptotic asymmetric-top O₃ molecule at 4000 and 5000 K are reported. The results are of significance for the studying of the molecular high-temperature spectrum including experimental measurements and theoretical calculations