A Theoretical Study of Monodeuteriation Effect on the Rearrangement of Trans-HCOH to H2CO via Quantum Tunneling with DFT and WKB Approximation

We study the effect of replacing hydrogen atom with deuterium (monodeuteriation) on the stability of trans-HCOH using density functional theory. The study begins by verifying that the monodeuteriation does not affect the electronic structure, but it does the vibrational frequency of the molecule. The potential barrier function is predicted using intrinsic reaction coordinate calculation and we use the predicted potential function to calculate the quantum tunneling probability using Wentzel-Kramers-Brillouin(WKB)approximation. We demonstrate the monodeuteration decreases the molecule's vibrational frequency as well as the quantum tunneling probability. The half-life calculation after monodeuteration is 2.97 × 1016 hours, which is extremely longer than before monodeuteration that is only 2.5 hours using the same calculation methods.