Theoretical Evidence for a Stable form of Cyclic Ozone, and its Chemical Consequences

1973 ◽  
Vol 51 (1) ◽  
pp. 139-146 ◽  
Author(s):  
James S. Wright
Keyword(s):  
Configuration Interaction ◽  
Pulse Radiolysis ◽  
Molecular Orbital Calculation ◽  
Low Energy ◽  
Basis Set ◽  
Slater Type Orbitals ◽  
Stable Form ◽  
Cyclic Form ◽  
Theoretical Evidence ◽  
Single Configuration

The total energy of the symmetrical, bent O3 molecule is studied as a function of internuclear angle and internuclear distance. The method used is an ab initio molecular orbital calculation with a minimum basis set of Slater-type orbitals, plus limited configuration interaction. Best single configuration energies show the existence of two stable minima: a cyclic (60°) structure and a bent (115°) structure. The cyclic structure is preferred by 48 kcal/mol, contrary to experiment (116° 48′) Configuration interaction results with two low lying orbitals show the cyclic form still preferred by 6 kcal/mol. A transition state for the bent-cyclic pathway lies 26 kcal/mol (or less) above the bent form. Based on these results, a possible low energy path via the cyclic form is proposed for the thermal decomposition of ozone. It is also proposed that cyclic ozone may have been observed in the pulse radiolysis of oxygen.

Assignment of the Low Energy Photoelectron Spectrum of the Octa-Sulphur Molecule: An ab initio Configuration Interaction Study

1983 ◽  
Vol 38 (12) ◽  
pp. 1359-1361 ◽  
Author(s):  
Michael H. Palmer
Keyword(s):  
Ab Initio ◽  
Configuration Interaction ◽  
Photoelectron Spectrum ◽  
Low Energy ◽  
Basis Set ◽  
Interaction Study ◽  
Orbital Ordering ◽  
Ionisation Potential ◽  
Koopmans Theorem ◽  
First Time

Abstract A large basis set ab initio configuration interaction study of S 8 has yielded a satisfactory assignment of the first 5 IP's of the UV-photoelectron spectrum for the first time. The ionisation potential order (low to high) is 2A1, 2E3, 2E2, 2E1 ≪2B2 and follows the orbital ordering of our recent large basis spd calculation, via the application of Koopmans' theorem.

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

2020 ◽  
Vol 2020 ◽  
pp. 1-6
Author(s):  
Shuang-Ling Tang ◽  
Yu Wang ◽  
Qi-Ying Xia ◽  
Xue-Hai Ju
Keyword(s):  
Configuration Interaction ◽  
Density Functional ◽  
Least Square Method ◽  
Potential Functions ◽  
Least Square ◽  
Basis Set ◽  
Dissociation Energies ◽  
Anharmonicity Constant ◽  
Different Temperatures ◽  
Relationship Of

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.

Convergence of Breit–Pauli spin–orbit matrix elements with basis set size and configuration interaction space: The halogen atoms F, Cl, and Br

2000 ◽  
Vol 112 (13) ◽  
pp. 5624-5632 ◽  
Author(s):  
Andreas Nicklass ◽  
Kirk A. Peterson ◽  
Andreas Berning ◽  
Hans-Joachim Werner ◽  
Peter J. Knowles
Keyword(s):  
Configuration Interaction ◽  
Interaction Space ◽  
Basis Set ◽  
Spin Orbit ◽  
Matrix Elements ◽  
Set Size ◽  
Halogen Atoms

Recalculation Yielded the Small Molecule Fragments of C3H6+ from Low Excited States of C5H8O+

2014 ◽  
Vol 513-517 ◽  
pp. 299-302
Author(s):  
Ying Zhu ◽  
Hong Bin Chen ◽  
Jie Wu
Keyword(s):  
Excited State ◽  
Excited States ◽  
Small Molecule ◽  
Vibration Frequency ◽  
Configuration Interaction ◽  
Basis Set ◽  
State Structure

Using the CIS(Configuration Interaction with Single Substitute) method, and 6-31+G (d, p) basis set, we calculated the excited state structure and vibration frequency of cyclopentanone ion. Studies on the possible way of obtain C3H6+ small fragments by cyclopentanone ion.

Ab Initio Studies on Amides: Pyrrolidin-2-one (γ-Butyrolactam)

1985 ◽  
Vol 38 (11) ◽  
pp. 1585 ◽  
Author(s):  
NV Riggs
Keyword(s):  
Ab Initio ◽  
Energy Cost ◽  
Equilibrium Structure ◽  
Ring Structure ◽  
Low Energy ◽  
Basis Set ◽  
Reference Plane ◽  
Envelope Conformation

By optimization with the 3-21G basis set, pyrrolidin-2-one is found clearly to prefer an envelope conformation with the flap bent 27.4° out of the NC(=O)C reference plane. The ring may be bent or twisted through a few degrees at low energy-cost, and undergoes rapid inversion through a planar-ring structure lying only 3.3 kJ mol-1 above the preferred equilibrium structure.

Vibrational spectroscopic and conformational studies of 1-(4-pyridyl)piperazine

2010 ◽  
Vol 64 (4) ◽  
Author(s):  
Özgür Alver ◽  
Mustafa Şenyel
Keyword(s):  
Density Functional ◽  
Structural Parameters ◽  
Density Functional Theory Method ◽  
Basis Set ◽  
Stable Form ◽  
Functional Theory ◽  
B3lyp Method ◽  
Ft Ir ◽  
Hybrid Density Functional ◽  
Ir And Raman

AbstractPossible stable conformers of the 1-(4-pyridyl)piperazine (1-4pypp) molecule were experimentally and theoretically studied by FT-IR and Raman spectroscopy. FT-IR and Raman spectra were recorded in the region of 4000–200 cm−1. Optimized geometric structures related to the minimum on the potential energy surface were investigated by the B3LYP hybrid density functional theory method using the 6-31G(d) basis set. Comparison of the experimental and theoretical results indicates that the density functional B3LYP method provides satisfactory results for the prediction of vibrational wavenumbers and structural parameters and equatorial-equatorial (e-e) isomer is supposed to be the most stable form of the 1–4pypp molecule.

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