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

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.

scholarly journals Secondary channels in the thermal decomposition of monomethylhydrazine (CH3NHNH2)

RSC Advances ◽  
2014 ◽  
Vol 4 (108) ◽  
pp. 62951-62964 ◽  
Author(s):  
Peng Zhang ◽  
Stephen J. Klippenstein ◽  
Lawrence B. Harding ◽  
Hongyan Sun ◽  
Chung K. Law
Keyword(s):  
Thermal Decomposition ◽  
Potential Energy ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Molecular Decomposition

The possible role of molecular decomposition channels in MMH is explored through additional investigations on triplet channels, roaming radical channels, and previously unexplored pathways on the potential energy surface.

scholarly journals Ultracold O2 + O2 collisions in a magnetic field: On the role of the potential energy surface

2011 ◽  
Vol 134 (12) ◽  
pp. 124310 ◽  
Author(s):  
Jesús Pérez-Ríos ◽  
José Campos-Martínez ◽  
Marta I. Hernández
Keyword(s):  
Magnetic Field ◽  
Potential Energy ◽  
Potential Energy Surface ◽  
Energy Surface

scholarly journals The Bifurcations of the Critical Points and the Role of Depth in a Symmetric Caldera Potential Energy Surface

2021 ◽  
Vol 31 (11) ◽  
pp. 2130034
Author(s):  
Y. Geng ◽  
M. Katsanikas ◽  
M. Agaoglou ◽  
S. Wiggins
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Critical Points ◽  
Energy Surface ◽  
The Other ◽  
Different Types ◽  
Before And After ◽  
The One ◽  
The Way

In this work, we continue the study of the bifurcations of the critical points in a symmetric Caldera potential energy surface. In particular, we study the influence of the depth of the potential on the trajectory behavior before and after the bifurcation of the critical points. We observe two different types of trajectory behavior: dynamical matching and the nonexistence of dynamical matching. Dynamical matching is a phenomenon that limits the way in which a trajectory can exit the Caldera based solely on how it enters the Caldera. Furthermore, we discuss two different types of symmetric Caldera potential energy surface and the transition from the one type to the other through the bifurcations of the critical points.

scholarly journals The Role of Supramolecular Intermediates in the Potential Energy Surface of the Diels-Alder Reaction

2017 ◽  
Vol 57 (4) ◽  
Author(s):  
Karla Ramírez-Gualito ◽  
Néstor López-Mora ◽  
Hugo A. Jiménez-Vázquez ◽  
Joaquín Tamariz ◽  
Gabriel Cuevas
Keyword(s):  
Maleic Anhydride ◽  
Potential Energy ◽  
Potential Energy Surface ◽  
Energy Surface ◽  
Van Der Waals ◽  
Cycloaddition Reaction ◽  
Alder Reaction ◽  
Diels Alder ◽  
Electrostatic Phenomena

The potential energy surface of four stereoselective Diels-Alder reactions was studied, namely: cyclopentadiene-maleic anhydride, furan-maleic anhydride, the dimerization of cyclopentadiene, and cyclopentadiene-cyclopropene. For completeness, we also studied the reaction between ethylene and 2-hydroxy-6-methyl-1,4-benzoquinone, a [5+2] cycloaddition reaction. For all cases at least a stationary state of supramolecular nature a van der Waals complex, was determined. These stationary states are complexes formed by the interaction between the reagents, minima located in the paths between the non-interacting molecules and the transition states. The existence of these complexes makes it necessary to reconsider the role of Secondary Orbital Interactions in the selectivity of these reactions. As it is the case with other complexes, the stability of these supramolecular intermediates depends on electrostatic phenomena such as dispersion forces. The observation of [5+2] intramolecular complexes in solution is important since up to now, this kind of van der Waals complexes had only been described in the gas phase.

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