The Potential Energy Surface of Guanine Is Not Flat:  Anab InitioStudy with Large Basis Sets and Higher Order Electron Correlation Contributions

1998 ◽  
Vol 102 (13) ◽  
pp. 2357-2362 ◽  
Author(s):  
Jerzy Leszczynski
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Electron Correlation ◽  
Energy Surface ◽  
Higher Order ◽  
Basis Sets

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.

scholarly journals Combining EXAFS and Computer Simulations to Refine the Structural Description of Actinyls in Water

Molecules ◽  
2020 ◽  
Vol 25 (22) ◽  
pp. 5250
Author(s):  
Sergio Pérez-Conesa ◽  
José M. Martínez ◽  
Rafael R. Pappalardo ◽  
Enrique Sánchez Marcos
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Force Field ◽  
Electron Correlation ◽  
Energy Surface ◽  
Open Shell ◽  
Complex Signal ◽  
Quantum Mechanical ◽  
Structural Description ◽  
Exafs Spectra

EXAFS spectroscopy is one of the most used techniques to solve the structure of actinoid solutions. In this work a systematic analysis of the EXAFS spectra of four actinyl cations, [UO2]2+, [NpO2]2+, [NpO2]+ and [PuO2]2+ has been carried out by comparing experimental results with theoretical spectra. These were obtained by averaging individual contributions from snapshots taken from classical Molecular Dynamics simulations which employed a recently developed [AnO2]2+/+ –H2O force field based on the hydrated ion model using a quantum-mechanical (B3LYP) potential energy surface. Analysis of the complex EXAFS signal shows that both An-Oyl and An-OW single scattering paths as well as multiple scattering ones involving [AnO2]+/2+ molecular cation and first-shell water molecules are mixed up all together to produce a very complex signal. Simulated EXAFS from the B3LYP force field are in reasonable agreement for some of the cases studied, although the k= 6–8 Å−1 region is hard to be reproduced theoretically. Except uranyl, all studied actinyls are open-shell electron configurations, therefore it has been investigated how simulated EXAFS spectra are affected by minute changes of An-O bond distances produced by the inclusion of static and dynamic electron correlation in the quantum mechanical calculations. A [NpO2]+−H2O force field based on a NEVPT2 potential energy surface has been developed. The small structural changes incorporated by the electron correlation on the actinyl aqua ion geometry, typically smaller than 0.07 Å, leads to improve the simulated spectrum with respect to that obtained from the B3LYP force field. For the other open-shell actinyls, [NpO2]2+ and [PuO2]2+, a simplified strategy has been adopted to improve the simulated EXAFS spectrum. It is computed taking as reference structure the NEVPT2 optimized geometry and including the DW factors of their corresponding MD simulations employing the B3LYP force field. A better agreement between the experimental and the simulated EXAFS spectra is found, confirming the a priori guess that the inclusion of dynamic and static correlation refine the structural description of the open-shell actinyl aqua ions.

A new potential energy surface of the OH2+ system and state-to-state quantum dynamics studies of the O+ + H2 reaction

2018 ◽  
Vol 20 (2) ◽  
pp. 1039-1050 ◽  
Author(s):  
Wentao Li ◽  
Jiuchuang Yuan ◽  
Meiling Yuan ◽  
Yong Zhang ◽  
Minghai Yao ◽  
...  
Keyword(s):  
Neural Network ◽  
Potential Energy ◽  
Potential Energy Surface ◽  
Configuration Interaction ◽  
Quantum Dynamics ◽  
Energy Surface ◽  
Basis Sets ◽  
Interaction Method ◽  
Configuration Interaction Method ◽  
Network Method

A new global potential energy surface of the O+ + H2 system was constructed with neural network method, using about 63000 ab initio points, which were calculated by employing the multi-reference configuration interaction method with aug-cc-pVTZ and aug-cc-pVQZ basis sets.

scholarly journals Rotational de-excitation of tricarbon monosulfide (C3S) in collision with (He): potential energy surface and rates

2020 ◽  
Vol 365 (12) ◽  
Author(s):  
E. Sahnoun ◽  
M. Ben Khalifa ◽  
F. Khadri ◽  
K. Hammami
Keyword(s):  
Potential Energy ◽  
Interstellar Medium ◽  
Potential Energy Surface ◽  
Cross Sections ◽  
Energy Surface ◽  
Accurate Determination ◽  
Carbon Chain ◽  
Basis Sets ◽  
Rate Coefficients

AbstractDespite that the tricarbon monosulfide (C3S) is among the first sulfur-containing carbon-chain molecules to be detected in the interstellar medium, no studies focused on the determination of its collisional rates. These rate coefficients are essential to estimate the abundance of C3S in the interstellar medium. Computations of the C3S($^{1}\Sigma^{+}$ Σ + 1 ) downward rate coefficients, induced by collision with He, are performed by averaging the integral cross sections at low temperature (below $25~\text{K}$ 25 K ). Calculations of the cross sections in the close-coupling quantum time independent formalism for $E_{c}\leq110~\text{cm}^{-1}$ E c ≤ 110 cm − 1 and $J\leq10$ J ≤ 10 are based on a new 2-D potential energy surface. This PES is obtained from the explicit correlated coupled cluster with a single, double and perturbative triple excitation [ccsd(t)-f12] ab initio approach and the aug-cc-pVTZ basis sets. The PES have a global minimum of $-55.69~\text{cm}^{-1}$ − 55.69 cm − 1 located at $R=6.25$ R = 6.25 bohr and $\theta=94^{\circ}$ θ = 94 ∘ , and a second minimum of $-36.95~\text{cm}^{-1}$ − 36.95 cm − 1 at $R=9.35$ R = 9.35 bohr and $\theta=0^{\circ}$ θ = 0 ∘ . A comparison of C3S rates with those of the isoelectronic molecule C3O was made. The results indicate a great temperature dependence of the rates for transitions of $\Delta J>2$ Δ J > 2 . We expect that the new collisional data will allow for accurate determination of the C3S abundance in several interstellar regions.

Understanding the hcp anisotropy in Cd and Zn: the role of electron correlation in determining the potential energy surface

2010 ◽  
Vol 12 (3) ◽  
pp. 681-687 ◽  
Author(s):  
Nicola Gaston ◽  
Dirk Andrae ◽  
Beate Paulus ◽  
Ulrich Wedig ◽  
Martin Jansen
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Electron Correlation ◽  
Energy Surface

Potential Energy Surface Including Electron Correlation for the Chemical F + H2 → FH + H I. Preliminary Surface

1972 ◽  
Vol 56 (9) ◽  
pp. 4626-4631 ◽  
Author(s):  
Charles F. Bender ◽  
Peter K. Pearson ◽  
Stephen V. O'Neil ◽  
Henry F. Schaefer
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Electron Correlation ◽  
Energy Surface
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