Analytic Morse/long-range potential energy surfaces and “adiabatic-hindered-rotor” treatment for a symmetric top-linear molecule dimer: A case study of CH3F–H2

Abstract

A first effective six-dimensional ab initio potential energy surface (PES) for CHF-H which explicitly includes the intramolecular Q stretching normal mode of the CHF monomer is presented. The electronic structure computations have been carried out at the explicitly correlated coupled cluster level of theory [CCSD(T)-F12a] with an augmented correlation-consistent triple zeta basis set. Five-dimensional analytical intermolecular PESs for ν(CHF) = 0 and 1 are then obtained by fitting the vibrationally averaged potentials to the Morse/Long-Range (MLR) potential function form. The MLR function form is applied to the nonlinear molecule-linear molecule case for the first time. These fits to 25 015 points have root-mean-square deviations of 0.74 cm and 0.082 cm for interaction energies less than 0.0 cm. Using the adiabatic hindered-rotor approximation, three-dimensional PESs for CHF-paraH are generated from the 5D PESs over all possible orientations of the hydrogen monomer. The infrared and microwave spectra for CHF-paraH dimer are predicted for the first time. These analytic PESs can be used for modeling the dynamical behavior in CHF-(H) clusters, including the possible appearance of microscopic superfluidity.

Calculating Entropies of Large Molecules in Aqueous Phase

“…An alternative to the method just described is the hindered rotor method, − which in principle provides a more accurate description but would be too computationally expensive.…”

An intramolecular vibrationally excited intermolecular potential energy surface and predicted 2OH overtone spectroscopy of H2O–Kr

“…The vibrationally averaged ab initio intermolecular potential energies Δ V̄ { v 1 , v 3 } ( R , Ω ) for H 2 O–Kr were fitted to a generalization of the three-dimensional (3D) MLR potential function form, 59–61 which is written as follows:in which, is the well depth and R e ( Ω ) is the position of the minimum on a radial cut through the potential at the angles Ω , while u LR ( R , Ω ) is a function which defines the (attractive) limiting long-range behaviour of the effective 1D potential along that cut asin which the long range coefficients C̄ n have also been averaged over the H 2 O vibrational coordinates Q 1 , and Q 3 with the intramolecular vibrational wave function ψ v 1 , v 3 ( Q 1 , Q 3 ) at a given state of ( v 1 , v 3 ). The denominator factor u LR ( R e , Ω ) is that same function evaluated at R = R e ( Ω ).…”

MLRNet: Combining the Physics-Motivated Potential Models with Neural Networks for Intermolecular Potential Energy Surface Construction

“…The recently developed Morse/long-range (MLR) model is a physics-motivated potential model for atom–atom interactions − that is flexible enough for midrange fitting while extrapolating in physically realistic behavior in the long- and short-distance regions. , Its extended version, the multidimensional MLR (mdMLR) model, has achieved success in fitting IPESs for atom–molecule − and molecule–molecule − systems within spectroscopic accuracy and retains the flexibility and sensible extrapolation that have been illustrated in dynamic simulations. − As with many other model potentials, the mdMLR model suffers from high-dimensional fitting problems, especially when intramolecular degrees of freedom are included . One efficient way is to average over the intramolecular vibrations under the weak coupling condition.…”