scholarly journals Theoretical and computational studies of non-equilibrium and non-statistical dynamics in the gas phase, in the condensed phase and at interfaces

2017 ◽  
Vol 375 (2092) ◽  
pp. 20170035 ◽  
Author(s):  
Riccardo Spezia ◽  
Emilio Martínez-Nuñez ◽  
Saulo Vazquez ◽  
William L. Hase
Keyword(s):  
Gas Phase ◽  
Condensed Phase ◽  
Potential Energy Surfaces ◽  
Molecular Mechanisms ◽  
Minimum Energy ◽  
Computational Studies ◽  
Statistical Dynamics ◽  
Reactive Trajectories ◽  
Energy Surfaces ◽  
Non Equilibrium

In this Introduction, we show the basic problems of non-statistical and non-equilibrium phenomena related to the papers collected in this themed issue. Over the past few years, significant advances in both computing power and development of theories have allowed the study of larger systems, increasing the time length of simulations and improving the quality of potential energy surfaces. In particular, the possibility of using quantum chemistry to calculate energies and forces ‘on the fly’ has paved the way to directly study chemical reactions. This has provided a valuable tool to explore molecular mechanisms at given temperatures and energies and to see whether these reactive trajectories follow statistical laws and/or minimum energy pathways. This themed issue collects different aspects of the problem and gives an overview of recent works and developments in different contexts, from the gas phase to the condensed phase to excited states. This article is part of the themed issue ‘Theoretical and computational studies of non-equilibrium and non-statistical dynamics in the gas phase, in the condensed phase and at interfaces’.

THEORETICAL STUDY ON THE H2 ACTIVATION BY PtO+ AND ${\rm PtO}_{2}^{+}$ IN THE GAS PHASE

2010 ◽  
Vol 09 (06) ◽  
pp. 963-974 ◽  
Author(s):  
YONGCHUN TONG ◽  
QINGYUN WANG ◽  
DONGQING WU ◽  
YONGCHENG WANG
Keyword(s):  
Potential Energy ◽  
Gas Phase ◽  
Potential Energy Surfaces ◽  
Density Functional ◽  
Reaction Pathway ◽  
Minimum Energy ◽  
Basis Sets ◽  
Avoided Crossing ◽  
Pass Through ◽  
Energy Surfaces

Gas-phase H2 activation by PtO+ and [Formula: see text] were studied at the density functional level of theory (DFT) using the relativistic effective core potential (RECP) of Stuttgart basis sets on platinum atom and UB3LYP/6-311+G(2d,2p) level on hydrogen and oxygen atoms. Two reaction profiles corresponding to the doublet and quartet multiplicities were investigated in order to ascertain the presence of some spin inversion during the H2 reduction. The electron-transfer reactivity of the reactions were analyzed using the two-state model, and the strongly crossing behavior on the transition state (TS) area were shown. Finally, the actions of frontier molecular orbitals in minimum-energy crossing point (MECP) have been illuminated briefly. These theoretical results can act as a guide to further theoretical and experimental research. H2 activation mediated by metal oxide cations were found to be an exothermic spin-forbidden process resulting from a crossing between quartet and doublet profiles. To evaluate the spin-forbidden process in the reaction pathway, the spin-obit coupling (SOC) matrix elements are calculated at the MECP with the different potential energy surfaces (PESs) and the probability of crossing between the adiabatic potential-energy surfaces during a single pass through the avoided crossing region was described. Therefore, the intersystem crossing (ISC) at crossing points (CP) occur efficiently because of the large SOC (ca. 85.58 cm-1) involved.

Serine–Ca2+ versus serine–Cu2+ complexes — A theoretical perspective

2010 ◽  
Vol 88 (8) ◽  
pp. 759-768 ◽  
Author(s):  
Al Mokhtar Lamsabhi ◽  
Otilia Mó ◽  
Manuel Yáñez
Keyword(s):  
Gas Phase ◽  
Electron Density ◽  
Potential Energy Surfaces ◽  
Metal Ion ◽  
Theoretical Perspective ◽  
Binding Energies ◽  
Interacting Systems ◽  
Intramolecular Hydrogen ◽  
Energy Surfaces ◽  
Doubly Charged

The association of Ca2+ and Cu2+ to serine was investigated by means of B3LYP DFT calculations. The [serine–M]2+ (M = Ca, Cu) potential energy surfaces include, as does the neutral serine, a large number of conformers, in which a drastic reorganization of the electron density of the serine moiety is observed. This leads to significant changes in the number and strength of the intramolecular hydrogen bonds existing in the neutral serine tautomers. In some cases, a proton is transferred from the carboxylic OH group to the amino group and accordingly, some of the more stable [serine–M]2+ complexes can be viewed as the result of the interaction of the zwiterionic form of serine with the doubly charged metal ion. Whereas the interaction between Ca2+ and serine is essentially electrostatic, that between Cu2+ and serine has a non-negligible covalent character, reflected in larger electron densities at the bond critical points between the metal and the base, in the negative values of the electron density between the two interacting systems, and in much larger Cu2+ than Ca2+ binding energies. More importantly, the interaction with Cu2+ is followed by a partial oxidation of the base, which is not observed when the metal ion is Ca2+. The main consequence is that in Cu2+ complexes a significant acidity enhancement of the serine moiety takes place, which strongly favors the deprotonation of the [serine–Cu]2+ complexes. This is not the case for Ca2+ complexes. Thus, [serine–Ca]2+ complexes, like those formed by urea, thiourea, selenourea, or glycine, should be detected in the gas phase. Conversely, the complexes with Cu2+ should deprotonate spontaneously and therefore only [(serine–H)–Cu]+ monocations should be experimentally accessible.

ChemInform Abstract: Synthesis of β-Lactams from Fluoroketenes and Imines: Ab initio Potential Energy Surfaces in Gas Phase and in Solution.

ChemInform ◽  
2010 ◽  
Vol 27 (40) ◽  
pp. no-no
Author(s):  
R. LOPEZ ◽  
M. F. RUIZ-LOPEZ ◽  
D. RINALDI ◽  
J. A. SORDO ◽  
T. L. SORDO
Keyword(s):  
Potential Energy ◽  
Ab Initio ◽  
Gas Phase ◽  
Potential Energy Surfaces ◽  
Energy Surfaces
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