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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: In this article, the authors present an ab initio direct dynamics study on the desorption of CO from semiquinone carbon−oxygen species in carbonaceous surfaces.
Abstract: We present an ab initio direct dynamics study on the desorption of CO from semiquinone carbon−oxygen species in carbonaceous surfaces. Density functional theory, in particular B3LYP/6-31G(d) level, was used to calculate the potential energy surface information. We found that in the initial stage of the desorption process, the six-member ring of the carbonaceous model opens slightly to let the CO break away, and then closes up to form the five-member ring. Because of low-lying excited estates in the carbon−oxygen complexes, electronic crossing occurs from reactants to products. Transition-state structures were found for the ground-state path, and the activation desorption energy is in excellent agreement with existing experimental data. Transition-state theory was used to calculate the thermal rate constant for desorption of CO in the range of 600−1700 °C. The fitted Arrhenius expression for the calculated rate constants is k(T) = 1.81 × 1017 exp[−47682/T(K)](s-1), which is within the experimental uncertai...
101 citations
TL;DR: Combining the dimer saddle point searching method and periodic density functional theory calculations, the potential energy surface of methanol decomposition on Cu(110) has been mapped out.
Abstract: Combining the dimer saddle point searching method and periodic density functional theory calculations, the potential energy surface of methanol decomposition on Cu(110) has been mapped out. Each elementary step in the methanol decomposition reaction into CO and hydrogen occurs via one of three possible mechanisms: O−H, C−H, or C−O bond scission. Multiple reaction pathways for each bond scission have been identified in the present work. Reaction pathway calculations are started from an initial (reactant) state with methanol adsorbed in the most stable geometry on Cu(110). The saddle point and corresponding final state of each reaction or diffusion mechanism were determined without assuming the reaction mechanism. In this way, the reaction paths are determined without chemical intuition. The harmonic pre-exponential factor of each identified reaction is calculated from a normal-mode analysis of the stationary points. Then, using harmonic transition state theory, the rate constant of each identified reaction...
101 citations
TL;DR: In this article, the potential energy surface of CH4-H2O is calculated through the fourth-order Mo/ller-Plesset perturbation theory, where the extended basis sets are augmented by bond functions which simulate the effects of high-symmetry polarization functions.
Abstract: The potential energy surface of CH4‐H2O is calculated through the fourth‐order Mo/ller–Plesset perturbation theory. In an attempt to obtain basis‐set saturated values of interaction energies the extended basis sets are augmented by bond functions which simulate the effects of high‐symmetry polarization functions. The absolute minimum occurs for the configuration involving the C–H‐O hydrogen‐bond in which O‐H points toward one of the faces of the CH4 tetrahedron. The equilibrium C–O separation is equal to 6.8 a0 which corresponds to the bond energy of 0.83 kcal/mol. Due to basis set unsaturation of the dispersion energy the bond energy may still be underestimated by about 0.05 kcal/mol. The secondary minimum involving the C‐H–O hydrogen‐bond is some 0.2 kcal/mol less stable, and the corresponding C–O distance is longer by 0.6 a0. The anisotropy of the potential energy surface is analyzed via the perturbation theory of intermolecular forces. The binding in CH4‐H2O is chiefly due to the dispersion energy whi...
101 citations
TL;DR: The adiabatic or Born-Oppenheimer approximation of molecular structure and dynamics has been widely used in the area of molecular physics and chemistry as discussed by the authors, where it has been used to explain a wide range of dynamical processes that lie outside its scope.
Abstract: At the heart of the quantum mechanical description of molecular structure and dynamics lies the adiabatic or Born-Oppenheimer approximation (1 , 2). Starting with an assumption of separability of time scales for nuclear and electronic motion, a familiar picture emerges of nuclei subject to well defined forces corresponding to the potential energy surface for a particular electronic state. Although the well-established success of these ideas in the areas of molecular spectroscopy (3-5) and reaction dynamics (6-9) is likely to secure the adiabatic approximation as a continuing foundation of molecular science, the range of dynamical processes that lies within its scope is far from complete. Recent experimental and theoretical advances in particular are beginning to yield a coherent understanding of several phenomena that, far from requiring minor corrections to the adiabatic approximation for their explanation, by their very nature exist entirely outside its framework. Examples of importance in diverse areas of chemistry and physics range from the dynamics of radiationless decay (1015) and nonadiabatic processes in chemical reactions (16-19) to the spectroscopy of excited (20-23) and ionized (24-26) states of isolated molecules, from single collision electronic energy transfer (27--41) to exciton (42) and soliton (43) dynamics and spin-lattice relaxation (44). Specialized reviews on these topics are available.
101 citations
TL;DR: In this article, the associative desorption of hydrogen atoms on graphite via an Eley-Rideal mechanism is studied theoretically, and time-independent quantum reactive scattering calculations are performed on a potential energy surface calculated using the generalised gradient approximation of density functional theory.
101 citations