Hardness profile of interaction of H–F with He, Ne and Ar: a density functional and MP2 calculation

In this study an attempt has been made to derive the chemical hardness and chemical potential profiles of Van der Waals complexes such as He–H–F, Ne–H–F and Ar–H–F using the MP2 method and hybrid density functional theory (DFT). It is observed that the hardness profiles of these complexes initially increase with increase in the reaction coordinate (Rg–H) and then decrease with the increase in the reaction coordinate. However, the hardness profiles of He–F–H, Ne–F–H and Ar–F–H increase with increase in the reaction coordinate (Rg–F) and then becomes constant with further increase in the reaction coordinate. This study has also demonstrated that hardness and chemical potential obtained from hybrid methods are lower when compared to the MP2 values. It is not possible to a draw definite correlation between the maximum hardness value and the equilibrium geometry of Van der Waals complexes. It is found that the principle of maximum hardness is not suitable for these complexes.