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Potential energy surface

About: Potential energy surface is a research topic. Over the lifetime, 11674 publications have been published within this topic receiving 307691 citations.


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TL;DR: It is concluded that a balanced description of the Fe 7s6p5d3f2g1h and N 4s3p1d partners is needed to reach convergence upon the potential energy surface descriptions and it is shown that the so‐called d′ orbitals allow for a significant charge redistribution along the transition.
Abstract: The importance of basis sets and active spaces in the determination of the potential energy curves and relevant energy differences in the O(h)-symmetry model system [Fe(NCH)(6)](2+) is analyzed using the Complete Active Space Self-Consistent Field (CASSCF) method and subsequent second-order perturbative treatment (CASPT2). By comparison of a series of atomic basis sets contraction, it is concluded that a balanced description of the Fe 7s6p5d3f2g1h and N 4s3p1d partners is needed to reach convergence upon the potential energy surface descriptions. Since the spin-crossover phenomenon involves the simultaneous change in the spin nature and expansion of the coordination sphere of the metal ion (i.e., lengthening of the Fe-N distances), the standard 10 electrons/12 orbitals complete active space is confronted to a chemically intuitive 18 electrons/15 orbitals picture. The role of a second d-shell is finally examined using the extended RAS strategy. Using a valence-bond type analysis, it is shown that the so-called d(') orbitals allow for a significant charge redistribution (approximately 0.5 electron) along the transition. Our calculations are compared to reference coupled-cluster estimations.

71 citations

Journal ArticleDOI
TL;DR: In this article, the N + N2 exchange rate is calculated using a time-dependent quantum dynamics method on a newly determined ab initio potential energy surface (PES) for the ground A" state.
Abstract: The N + N2 exchange rate is calculated using a time-dependent quantum dynamics method on a newly determined ab initio potential energy surface (PES) for the ground A" state. This ab initio PES shows a double barrier feature in the interaction region with the barrier height at 47.2 kcal/mol, and a shallow well between these two barriers, with the minimum at 43.7 kcal/mol. A quantum dynamics wave packet calculation has been carried out using the fitted PES to compute the cumulative reaction probability for the exchange reaction of N + N2(J=O). The J - K shift method is then employed to obtain the rate constant for this reaction. The calculated rate constant is compared with experimental data and a recent quasi-classical calculation using a LEPS PES. Significant differences are found between the present and quasiclassical results. The present rate calculation is the first accurate 3D quantal dynamics study for N + N2 reaction system and the ab initio PES reported here is the first such surface for N3.

71 citations

Journal ArticleDOI
TL;DR: In this article, a full potential energy surface for the excited state was constructed by means of ab initocluster calculations in addition to the ground state for the NiO(100) surface, and multidimensional wave packet calculations on these two surfaces allow a detailed simulation of experimental observations, such as velocity distributions and desorption probabilities, on a full ab initio basis.
Abstract: State resolved laser induced desorption of NO molecules from a NiO(100) surface is studiedtheoretically. A full potential energy surface for the excited state was constructed by means of ab initiocluster calculations in addition to the potential energy surface for the ground state. Multidimensionalwave packet calculations on these two surfaces allow a detailed simulation of experimentalobservables, such as velocity distributions and desorption probabilities, on a full ab initio basis.[S0031-9007(98)06374-1]

71 citations

Journal ArticleDOI
TL;DR: This analysis suggests that even though water is heterogeneous in terms of the number of hydrogen bonds, the coupling between neighbors on various length and time scales brings about greater continuity in its properties.
Abstract: A definition that equates a hydrogen bond topologically with a local energy well in the potential energy surface is used to study the structure and dynamics of liquid water. We demonstrate the robustness of this hydrogen-bond definition versus the many other definitions which use fixed, arbitrary parameters, do not account for variable molecular environments, and cannot effectively resolve transition states. Our topology definition unambiguously shows that most water molecules are double acceptors but sizable proportions are single or triple acceptors. Almost all hydrogens are found to take part in hydrogen bonds. Broken hydrogen bonds only form when two molecules try to form two hydrogen bonds between them. The double acceptors have tetrahedral geometry, lower potential energy, entropy, and density, and slower dynamics. The single and triple acceptors have trigonal and trigonal bipyramidal geometry and when considered together have higher density, potential energy, and entropy, faster dynamics, and a tendency to cluster. These calculations use an extended theory for the entropy of liquid water that takes into account the variable number of hydrogen bonds. Hydrogen-bond switching is shown to depend explicitly on the variable number of hydrogen bonds accepted and the presence of interstitial water molecules. Transition state theory indicates that the switching of hydrogen bonds is a mildly activated process, requiring only a moderate distortion of hydrogen bonds. Three main types of switching events are observed depending on whether the donor and acceptor are already sharing a hydrogen bond. The switch may proceed with no intermediate or via a bifurcated-oxygen or cyclic dimer, both of which have a broken hydrogen bond and symmetric and asymmetric forms. Switching is found to be strongly coupled to whole-molecule vibration, particularly for the more mobile single and triple acceptors. Our analysis suggests that even though water is heterogeneous in terms of the number of hydrogen bonds, the coupling between neighbors on various length and time scales brings about greater continuity in its properties.

71 citations

Journal ArticleDOI
TL;DR: The molecular structure of 2-(tert-butoxycarbonyl (Boc) -amino)-5-bromopyridine (BABP) was optimized by the DFT/B3LYP method and vibrational frequencies were assigned on the basis of Potential Energy Distribution (PED) calculation using the VEDA 4.0 program.

71 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023128
2022206
2021288
2020322
2019295
2018310