Bachelor final project

Title: The Calculation of Forces in Molecules using Hellmann-Feynman theorem

Supervisor: Dr. Teepanis Chachiyo

Abstract

An extension to Siam Quantum program^[1] was implemented to compute forces in molecules using Hellmann-Feynman theorem in which forces in molecules could be approximated using classical electrostatic theory. In order to find forces from the theory, electric potential and electric field have to be calculated earlier. The ground state wave function was obtained using Siam Quantum program and was used in finding electric potential. An extension to Siam Quantum program was made to calculate electric potential, electric field and forces in molecules. The calculated electric potential and electric field showed good agreement with the results from Gaussian03w with the errors of 0.005% and 0.795% respectively. However, the forces were not correct. Further literature reviews showed that the discrepancy might due to the nature of the basis function. Moreover, the correction term called Pulay force could be added for a more reliable calculation of the forces.

Keywords: Hellmann-Feynman forces, Siam Quantum

[1] https://sites.google.com/site/siamquantum/home?authuser=0