Behavior of HF and (HF)2 inside a fullerene cage: A benchmarking study
using different density functionals
Abstract
A proper benchmarking on the properties of HF and its dimer inside C60
using density functional theory (DFT) based approaches is presented. For
this purpose, 10 different DFT functionals following Jacob’s Ladder have
been chosen. Geometrical parameters, viz., bond length, bond angle,
etc., and dipole moment have been computed. Two types of orientations,
viz., L-shaped and anti-parallel of (HF)2 inside C60 are considered, the
latter with an extremely short hydrogen bond. HF bond lengths are
elongated upon encapsulation in comparison to its free state analogue.
The calculated stability of HF@C60 is functional dependent whereas,
(HF)2C60 is thermodynamically unstable for all the functionals. The
kinetic stability of (HF)2@C60 is observed through ADMP simulation at
300K temperature. The red shift in HF stretching frequencies is noticed
in all cases. NCI analysis exhibits a non-covalent type interaction
between HF dimer and the C60 cage. The total interaction energy is found
to be negative for HF@C60. EDA analysis showed a high value of repulsive
ΔEpauli which makes the (HF)2@C60 system unstable except for the
functional BP86-D3 of GGA family. Furthermore, QTAIM analysis is
performed and confirmed the presence of (3, -1) bond critical point
along the hydrogen bond region for L-shaped (HF)2C60.