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.

Quantum algorithm for obtaining the energy spectrum of molecular systems

Abstract: Simulating a quantum system is more efficient on a quantum computer than on a classical computer. The time required for solving the Schrodinger equation to obtain molecular energies has been demonstrated to scale polynomially with system size on a quantum computer, in contrast to the well-known result of exponential scaling on a classical computer. In this paper, we present a quantum algorithm to obtain the energy spectrum of molecular systems based on the multiconfigurational self-consistent field (MCSCF) wave function. By using a MCSCF wave function as the initial guess, the excited states are accessible. Entire potential energy surfaces of molecules can be studied more efficiently than if the simpler Hartree-Fock guess was employed. We show that a small increase of the MCSCF space can dramatically increase the success probability of the quantum algorithm, even in regions of the potential energy surface that are far from the equilibrium geometry. For the treatment of larger systems, a multi-reference configuration interaction approach is suggested. We demonstrate that such an algorithm can be used to obtain the energy spectrum of the water molecule.

Potential Energy Surface Including Electron Correlation for F + H2 → FH + H: Refined Linear Surface

Abstract: A priori quantum mechanical calculations have been carried out at about 150 linear geometries for the fluorine plus hydrogen molecule system An extended basis set of Gaussian functions was used, and electron correlation was treated explicitly by configuration interaction Comparison with the experimental activation energy and exothermicity suggests that the theoretical potential surface is quite realistic

Changes in the electronic structure and vibrational potential of hydrogen fluoride upon dimerization: A well‐correlated (HF)2 potential energy surface

Abstract: A large basis, coupled‐cluster level treatment of the electronic structure of the hydrogen fluoride dimer has been used to develop an accurate potential energy surface and dipole moment surface. The vibrational motion of the HF subunits was analyzed using a number of different methods for comparison with recent experimental results. Molecular properties averaged over the vibrational motion were also calculated. The vibrational transition frequencies for the two HF stretches in the dimer agree with experiment to 1%, while the shifts in these frequencies agree with experiment to 10 cm−1. The importance of higher order correlation effects and treatment of vibrational anharmonicities is made clear by these results. Transition moments were calculated and show enhancements for both HF stretches in the dimer.

Ridge method for finding saddle points on potential energy surfaces

Abstract: A new method is proposed for locating saddle points on potential energy surfaces. The method involves walking on the ridge separating reactants’ and products’ valleys toward its minimum, which is a saddle point in coordinate space. Of particular advantage for ab initio calculations, the ridge method does not require evaluation of second derivatives of the potential energy. Another important feature of the method is that no assumptions about the transition state geometry are needed, and it is easy to impose linear constraints on the molecular structure. The ridge method is supplemented by a heuristic detour algorithm, which enables one to deal with unfortunate choices of reactants’ and products’ coordinates. Both algorithms are illustrated by several examples where the complexity of the potential energy surface ranges from a simple analytical formula to a numerical many‐body ab initio potential.

Unimolecular reaction rate theory for transition states of any looseness. 3. Application to methyl radical recombination

Abstract: The theory for unimolecular reactions described in part 1 is applied to the recombination of methyl radicals in the high-pressure limit. The model potential energy surface and the methodology are briefly described. Results are presented for the recombination rate constant k_ ∞ at T = 300, 500, 1000, and 2000 K. Canonical and Boltzmann averaged microcanonical values of k_ ∞ are compared, and the influence of a potential energy interpolation parameter and a separation-dependent symmetry correction on k_ ∞ are examined. Earlier theoretical models and extensive experimental results are compared with the present results which are found to have a negative temperature dependence. The present results agree well with some of the available but presently incomplete experimental determinations of the high-pressure recombination rate constant for this reaction over the 300-2000 K temperature range. There is also agreement with a decomposition rate constant for a vibrationally excited ethane molecule produced by chemical activation.