Degenerate perturbation theory corrections for the vibrational self-consistent field approximation: Method and applications
نویسندگان
چکیده
A new algorithm for computing anharmonic vibrational states for polyatomic molecules is proposed. The algorithm starts with the vibrational self-consistent field ~VSCF! method and uses degenerate perturbation theory to correct for effects of correlation between different vibrational modes. The algorithm is developed in a version that computes the anharmonic vibrational spectroscopy directly from potential energy surface points calculated by using ab initio codes. The method is applied to several molecules where near degeneracies occur for excited vibrational states, including HOOH, HSSH, and HOOOH. The method yields results in very good accordance with experiments and generally provides improvements over nondegenerate perturbation corrections for VSCF. © 2002 American Institute of Physics. @DOI: 10.1063/1.1494978#
منابع مشابه
Calculating molecular vibrational spectra beyond the harmonic approximation
We present a new approach for calculating anharmonic corrections to vibrational frequency calculations. The vibrational wavefunction is modelled using translated Hermite functions thus allowing anharmonic effects to be incorporated directly into the wavefunction whilst still retaining the simplicity of the Hermite basis. We combine this new method with an optimised finite-difference grid for co...
متن کاملSelf-consistent-field Perturbation Theory for the Schrr Odinger Equation Typeset Using Revt E X 1
A method is developed for using large-order perturbation theory to solve the systems of coupled diierential equations that result from variational solution of the Schrr odinger equation with wavefunctions of product form. This is a noniterative, computationally eecient way to solve self-consistent-eld (SCF) equations. Possible applications include electronic structure calculations using product...
متن کاملVariational calculation of vibrational linear and nonlinear optical properties.
A variational approach for reliably calculating vibrational linear and nonlinear optical properties of molecules with large electrical and/or mechanical anharmonicity is introduced. This approach utilizes a self-consistent solution of the vibrational Schrodinger equation for the complete field-dependent potential-energy surface and, then, adds higher-level vibrational correlation corrections as...
متن کاملThe NMR indirect nuclear spin–spin coupling constants for some small rigid hydrocarbons: molecular equilibrium values and vibrational corrections
The indirect nuclear spin–spin coupling constants of allene and of two sterically strained hydrocarbons – cyclopropane and cyclopropene – calculated at different levels of electronic-structure theory are compared with each other and with experimental equilibrium constants, obtained from experiment by subtracting calculated vibrational contributions. It is found that, even in a relatively small ...
متن کاملPull-in behavior analysis of vibrating functionally graded micro-cantilevers under suddenly DC voltage
The present research attempts to explain dynamic pull-in instability of functionally graded micro-cantilevers actuated by step DC voltage while the fringing-field effect is taken into account in the vibrational equation of motion. By employing modern asymptotic approach namely Homotopy Perturbation Method with an auxiliary term, high-order frequency-amplitude relation is obtained, then the infl...
متن کامل