Potential Functions and Thermodynamic Properties of UC, UN, and UH

Potential energy surface scanning for UC, UN, and UH was performed by configuration interaction (CI), coupled cluster singles and doubles (CCSD) excitation, quadratic configuration interaction (QCISD (T)), and density functional theory PBE1 (DFT-PBE1) methods in coupling with the ECP80MWB_AVQZ + 2f basis set for uranium and 6 − 311 + G∗ for carbon, hydrogen, and nitrogen. The dissociation energies of UC, UN, and UH are 5.7960, 4.5077, and 2.6999 eV at the QCISD (T) levels, respectively. The calculated energy was fitted to the potential functions of Morse, Lennard-Jones, and Rydberg by using the least square method. The anharmonicity constant of UC is 0.0047160. The anharmonic frequency of UC is 780.27 cm−1 which was obtained based on the PBE1 results. For UN, the anharmonicity constant is 0.0049827. The anharmonic frequency is 812.65 cm−1 which was obtained through the PBE1 results. For UH, the anharmonicity constant is 0.017300. The anharmonic frequency obtained via the QCISD (T) results is 1449.8 cm−1. The heat capacity and entropy in different temperatures were calculated using anharmonic frequencies. These properties are in good accordance with the direct DFT-UPBE1 results (for UC and UN) and QCISD (T) results (for UH). The relationship of entropy with temperature was established.

Interatomic Potential and Thermodynamic Property of Diatomic Uranium

Potential energy scan for U2 was performed by density functional theory (DFT) method at the B3LYP level in combination with the (ECP80MWB_AVQZ + 2f) basis set. The dissociation energy of U2, after being corrected for the zero-point vibrational energy, is 2.482 eV, which is in good agreement with the experiment. The calculated energy was fit to the typical potential functions of Morse, Lennard-Jones (L-J) and Rydberg. Both the Morse and Rydberg functions are good representatives of the potentials, but the Lennard-Jones function is not. The anharmonicity constant is very small. The anharmonic frequency is 113.99 cm–1. Thermodynamic properties of entropy and heat capacity at 298.2 K – 1500 K were calculated by using DFT-B3LYP computational results and Morse parameters, respectively. The relationship between entropy and temperature was established.

GROUP 12 ELEMENTS AND THEIR SMALL CLUSTERS: ELECTRIC DIPOLE POLARIZABILITY OFZn,CdANDHg,Zn2DIMER AND HIGHERZnnMICROCLUSTERS AND NEUTRAL, CATIONIC AND ANIONIC ZINC OXIDE MOLECULES (ZnO,ZnO+ANDZnO-)

This review is in general about group 12 elements and their small microclusters. In this part, after presenting an extensive literature survey of the electric dipole polarizability studies of the Zn , Cd and Hg atoms, we specifically target zinc-containing small clusters, beginning with the Zn2dimer, the Zn3trimer, higher Znnclusters and the neutral, cationic and anionic zinc oxide clusters: ZnO , ZnO+and ZnO-. We tabulated experimental and theoretical results for the spectroscopic constants (dissociation energy Deor D0, bond length re, fundamental frequency we, anharmonicity constant wexeand dipole moment μe) of the diatomic clusters and the first and second ionization potentials IP1and IP2and electron affinity EA of the species reviewed.

Interpretation of Vapor-Liquid Frequency Shift of CH stretching vibration of chloroform and Fluoroform

The change in the frequency of the CH stretching vibration and in its anharmonicity constant, quadratic, cubic and quartic force constants and the equilibrium CH bond distance, on condensation, were investigated by performing model calculations for liquid chloroform and fluoroform. The interactions between the hydrogen atom and the CH oscillator, represented by a Morse potential, and the halogen atoms of its neighbor molecules were described by the sum of Lennard- Jones and Coulomb potential functions employed in molecular dynamics simulation. The calculations were carried out for different molecular arrangements in the liquid and have shown that mainly the size of the halogen atom, consequently the intermolecular distances, govern the direction of the CH vibrational frequency shift and of the change in the anharmonicity constant on the vapor-liquid transition. The pressure and temperature dependence of the CH stretching vibration was also studied for liquid chloroform. While the calculated pressure dependence is in good agreement with that observed, only the direction of the temperature dependence is in accordance with experimental observation.

Application of Vapor Pressure Isotope Effect to the Determinationof Vibrational Anharmonicity in the Liquid Phase

The experimentally observed H/D vapor pressure isotope effects in chloroform and bromoform were combined with reliable spectroscopic data from the literature in order to obtain information on the change of the potential curve of the CH stretching motion on vapor-liquid transition. The parameters studied include the Morse potential parameters, the anharmonicity constant and the harmonic, cubic and quartic force constants in both phases. While the anharmonic character of the potential energy curve of the CH oscillator of chloroform has been found to decrease on condensation. the opposite behavior has been observed in the case of bromoform.

Vapour Pressure Isotope Effects of Chloroform

The vapour pressure difference between CHCl3 and CDCl3 is measured by differential capacitance manometry between -60 and +60 °C. The results can be expressed by the equation ln(pH /pD) = 5.507 × 10-3-6.269/T. The vapour pressure of CHCl3 between -98 and +62°C has also been determined. The experimental H/D vapour pressure isotope effect data together with the available literature values on the 12C/13C and 35C1/37Cl isotope effects are interpreted within the framework of the statistical mechanical theory of isotope effects in condensed systems. The results show that the anharmonicity constant of the CH stretching vibration decreases by about 4% on the vapour-liquid transition.