README.md

MP2 potential energy surface of HeH2p

Authors: L.I. Vazquez-Salazar and M. Meuwly

This repository contains the data to construct the potential energy surface at MP2 level with the basis set aug-cc-pVTZ for the HeH_{2}^{+} system.

Ab initio calculations

The data is saved in the file pes_mp2.csv. The first column is the value of the angle (as $angle = 1-cos(\theta)/2$, second is the coordinate $R$, third is the coordinate $r$ and the last column is the value of the energy in eV. To fit the PES, you need the RKHS package that can be found in RKHS. To do the fitting of the PES follow instructions there.

Evaluation of the PES

Complementary, a pes_mp2.kernel file containing the coefficients of the kernel fitting is provided. This file can be used to evaluate the potential energy surface using the RKHS package. The file evaluate_kernel.f90 contains the code to evaluate the PES in a defined grid $\theta \in [0,180]$, $r \in [0,10]$ and $R \in [0,20]$. The file evalute_kernel.f90 can be compiled with the adjunct make file. It requires the RKHS module in the same directory. The output will be evaluate_kernel.x that can be executed as follows

./evaluate_kernel.x pes_mp2.kernel new_pes.csv

Which will create a file new_pes.csv with the values of the PES in the defined grid.

Fitting of 2-body potentials

The potential for HeH+ and H2+ are fitted following the analytical expression in: Phys.Chem.Chem.Phys. 2019, 21, 24976. In the folder Diatomic, the file fitting.py can be used to obtain the coefficients of the analytical expression. A plot with the correlation plot and the fitting of the curve will be showed. The file h2p.csv contains the data for the H2+ system and heh2p.csv contains the data for the HeH+ system.

Contact

For any questions, please contact Markus Meuwly ([email protected]) or Luis Vazquez-Salazar ([email protected])