scholarly journals Structures and stabilities of C2H2F3+ cations: an abinitio molecular orbital study

1987 ◽  
Vol 65 (3) ◽  
pp. 473-481 ◽  
Author(s):  
Micheline Charpentier ◽  
Jacques Fossey ◽  
Thomas T. Tidwell ◽  
Saul Wolfe
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Atomic Orbital ◽  
Minimum Energy ◽  
Saddle Points ◽  
Lone Pair ◽  
Basis Set ◽  
Stationary Points ◽  
Energy Structure

Eleven stationary points on the singlet C2H2F3+ potential energy surface have been calculated using the 3-21G basis set, and characterized as minima (four structures) or first-order saddle points (seven structures) by vibrational analysis. To check the reliability of this basis set, three of the structures have also been optimized at the 6-31G* level; although the geometries change somewhat, the relative energies and nature (maxima, minima) of the structures remain the same. For CF3CH2+ the minimum energy structure has one C—F bond coplanar with the vacant p-atomic orbital at the cationic centre. The structure is 16.4 kcal/mol less stable than the lowest energy conformation of FCH2CF2+, and the barrier for the 1,2 fluorine migration which connects the two structures is low. The cation F2CHCHF+ has a conformation that is a minimum on the potential energy surface that is 16.9 kcal/mol higher in energy than FCH2CF2+; the two structures are separated by a barrier for 1,2 hydrogen migration of 23.5 kcal/mol. The electronic effects in the various structures have been studied using a quantitative PMO analysis of the interactions between the two carbon fragments of the ions. For CF3CH2+ the net effect of the fluorine is highly destabilizing; the principal stabilizing interactions between CF3+ and CH2 consist of π donation from CF3+ to CH2 and homoconjugation of a fluorine lone pair with the cationic centre. No net stabilization attributable to fluorine bridging could be found.

scholarly journals Improved Potential Energy Surface of Ozone Constructed Using the Fitting by Permutationally Invariant Polynomial Function

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Mehdi Ayouz ◽  
Dmitri Babikov
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Polynomial Function ◽  
Minimum Energy ◽  
Basis Set ◽  
Invariant Polynomial ◽  
Complete Basis Set ◽  
Data Points ◽  
Small Set

New global potential energy surface for the ground electronic state of ozone is constructed at the complete basis set level of the multireference configuration interaction theory. A method of fitting the data points by analytical permutationally invariant polynomial function is adopted. A small set of 500 points is preoptimized using the old surface of ozone. In this procedure the positions of points in the configuration space are chosen such that the RMS deviation of the fit is minimized. New ab initio calculations are carried out at these points and are used to build new surface. Additional points are added to the vicinity of the minimum energy path in order to improve accuracy of the fit, particularly in the region where the surface of ozone exhibits a shallow van der Waals well. New surface can be used to study formation of ozone at thermal energies and its spectroscopy near the dissociation threshold.

Rotational de-excitations of C3H+ (1Σ+) by collision with He: new ab initio potential energy surface and scattering calculations

2020 ◽  
Vol 494 (4) ◽  
pp. 5675-5681 ◽  
Author(s):  
Sanchit Chhabra ◽  
T J Dhilip Kumar
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Ab Initio ◽  
Cross Sections ◽  
Energy Surface ◽  
Molecular Ions ◽  
Basis Set ◽  
Rate Coefficients ◽  
Close Coupling ◽  
Collisional Rate Coefficients

ABSTRACT Molecular ions play an important role in the astrochemistry of interstellar and circumstellar media. C3H+ has been identified in the interstellar medium recently. A new potential energy surface of the C3H+–He van der Waals complex is computed using the ab initio explicitly correlated coupled cluster with the single, double and perturbative triple excitation [CCSD(T)-F12] method and the augmented correlation consistent polarized valence triple zeta (aug-cc-pVTZ) basis set. The potential presents a well of 174.6 cm−1 in linear geometry towards the H end. Calculations of pure rotational excitation cross-sections of C3H+ by He are carried out using the exact quantum mechanical close-coupling approach. Cross-sections for transitions among the rotational levels of C3H+ are computed for energies up to 600 cm−1. The cross-sections are used to obtain the collisional rate coefficients for temperatures T ≤ 100 K. Along with laboratory experiments, the results obtained in this work may be very useful for astrophysical applications to understand hydrocarbon chemistry.

THE H2NO POTENTIAL ENERGY SURFACE EXPLORED WITH HIGH LEVEL AB INITIO AND DENSITY FUNCTIONAL THEORY METHODS

2007 ◽  
Vol 06 (03) ◽  
pp. 549-562
Author(s):  
ABRAHAM F. JALBOUT
Keyword(s):  
Density Functional Theory ◽  
Potential Energy ◽  
Potential Energy Surface ◽  
Density Functional ◽  
Energy Surface ◽  
Hybrid Methods ◽  
Transition States ◽  
Basis Set ◽  
Functional Theory ◽  
High Level

The transition states for the H 2 NO decomposition and rearrangements mechanisms have been explored by the CBS-Q method or by density functional theory. Six transition states were located on the potential energy surface, which were explored with the Quadratic Complete Basis Set (CBS-Q) and Becke's one-parameter density functional hybrid methods. Interesting deviations between the CBS-Q results and the B1LYP density functional theory lead us to believe that further study into this system is necessary. In the efforts to further assess the stabilities of the transition states, bond order calculations were performed to measure the strength of the bonds in the transition state.

The search for stationary points on a quantum mechanical/molecular mechanical potential-energy surface

2002 ◽  
Vol 107 (3) ◽  
pp. 147-153 ◽  
Author(s):  
Xavier Prat-Resina ◽  
Mireia Garcia-Viloca ◽  
Gerald Monard ◽  
Angels González-Lafont ◽  
José M. Lluch ◽  
...  
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Stationary Points ◽  
Quantum Mechanical

scholarly journals Accurate global potential energy surface for the ground state of CH2+ by extrapolation to the complete basis set limit

RSC Advances ◽  
2018 ◽  
Vol 8 (25) ◽  
pp. 13635-13642 ◽  
Author(s):  
Lu Guo ◽  
Hongyu Ma ◽  
Lulu Zhang ◽  
Yuzhi Song ◽  
Yongqing Li
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Ground State ◽  
Energy Surface ◽  
Correlation Energy ◽  
Basis Set ◽  
Basis Sets ◽  
Complete Basis ◽  
Complete Basis Set ◽  
Complete Basis Set Limit

A full three-dimensional global potential energy surface is reported for the ground state of CH2+ by fitting accurate multireference configuration interaction energies calculated using aug-cc-pVQZ and aug-cc-pV5Z basis sets with extrapolation of the electron correlation energy to the complete basis set limit.

Potential energy surface stationary points and dynamics of the F−+ CH3I double inversion mechanism

2017 ◽  
Vol 19 (30) ◽  
pp. 20127-20136 ◽  
Author(s):  
Yong-Tao Ma ◽  
Xinyou Ma ◽  
Anyang Li ◽  
Hua Guo ◽  
Li Yang ◽  
...  
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Stationary Points ◽  
Direct Dynamics ◽  
Dynamics Simulations ◽  
Inversion Mechanism

Direct dynamics simulations were performed to study the SN2 double inversion mechanism SN2-DI, with retention of configuration, for the F−+ CH3I reaction.

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