Potential Energy Surface Function Research Articles

Classification of the HCN isomerization reaction dynamics in Ar buffer gas via machine learning.

The effect of the presence of Ar on the isomerization reaction HCN ⇄ CNH is investigated via machine learning. After the potential energy surface function is developed based on the CCSD(T)/aug-cc-pVQZ level abinitio calculations, classical trajectory simulations are performed. Subsequently, with the aim of extracting insights into the reaction dynamics, the obtained reactivity, that is, whether the reaction occurs or not under a given initial condition, is learned as a function of the initial positions and momenta of all the atoms in the system. The prediction accuracy of the trained model is greater than 95%, indicating that machine learning captures the features of the phase space that affect reactivity. Machine learning models are shown to successfully reproduce reactivity boundaries without any prior knowledge of classical reaction dynamics theory. Subsequent analyses reveal that the Ar atom affects the reaction by displacing the effective saddle point. When the Ar atom is positioned close to the N atom (resp. the C atom), the saddle point shifts to the CNH (HCN) region, which disfavors the forward (backward) reaction. The results imply that analyses aided by machine learning are promising tools for enhancing the understanding of reaction dynamics.

A model for the dissociative adsorption of N2O on Cu(100) using a continuous potential energy surface

For the first time, a continuous ab initio potential energy surface (PES) taking into account all molecular degrees of freedom is built and used to model the reaction of a polyatomic molecule with a surface. DFT slab calculations are used to sample the configuration space of the system N2O/Cu(1 0 0), and the PES function is built with a method of Manzhos and Carrington [J. Chem. Phys. 127 (2007) 014103] using dimensionality reduction from only 4300 single-point energies. Molecular dynamics simulations are performed on the PES to calculate the probability of dissociative adsorption.

The nature of intramolecular hydrogen bond in 2-nitromalonaldehyde

Abstract A simple, practical method for treating the proton tunneling in 2-nitromalonaldehyde (NO2MA) was used. A two-dimensional potential energy surface (PES) function, which couples OH stretching and in-plane bending modes, has been constructed for motions of the hydrogen atom by the aid of quantum mechanical calculations at the MP2/6-31G** level for a fixed skeleton geometry. This PES function was used to calculate energy levels, from which a tunneling splitting of 34.5 and 3.2 cm−1 was obtained for light and deuterated NO2MA, respectively, in excellent agreement with the experimental value of 35.0 ± 15.0 and 3.0 ± 0.02 cm−1, respectively. The double-well barrier height was predicted to be 46.4 kJ/mol with respect to the midpoint between the two adjacent minima of the hydrogen motions on the PES. The hydrogen-bond strength was estimated to be over 50 kJ/mol.