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

Abstract

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.

Empirical quality criteria for the approximation of the electronic term of a diatomic molecule by the Morse formula

“…The Morse model potential [1], despite a very rough approximation, is widely used in molecular spectroscopy and in other areas of optics and chemical physics. According to the Chemical Abstracts Service, over 6,000 references are given on the request " Morse Formula" Ȧs an example, we present random selections of recent studies in the field of spectroscopy [2][3][4][5][6][7][8][9][10][11][12][13], the influence of an external field, laser dissociation of moleculescool [14][15][16][17][18][19][20][21][22][23][24], thermodynamics, kinetics [25][26][27][28][29][30][31][32][33][34], solid and liquid physicssti [35][36][37][38][39][40][41][42][43][44], intermolecular interactions [45][46][47]…”

Эмпирические Критерии Качества Аппроксимации Электронного Терма Двухатомногой Молекулы Формулой Морза

“…По данным химической реферативной службы (Chemical Abstracts Service) на запрос " Формула Морза" выдаётся более 6000 ссылок. Как пример, приведём случайные выборки работ последнего времени в области спектроскопии [2][3][4][5][6][7][8][9][10][11][12][13], влияния внешнего поля, лазерной диссоциации молекул [14][15][16][17][18][19][20][21][22][23][24], термодинамики, кинетики [25][26][27][28][29][30][31][32][33][34], физики твёрдого тела и жидкости [35][36][37][38][39][40][41][42][43][44], межмолекулярных взаимодействий [45][46][47][48][49][50]…”