A novel theoretical study of thermally-induced reaction and vibration dynamics of methanol dissociative adsorption onto a Si(001) surface

The thermally-induced reaction and vibration dynamics of methanol (CH3OH(g)) dissociative adsorption onto a Si(001) surface have been studied by combining density functional theory (DFT)-based molecular dynamics (DFTMD) simulations with a molecular adsorption sampling scheme and a wavelet transform for investigating the reaction pathways and corresponding vibrational spectra. Based on the simulated results, CH3OH(g) firstly approaches the Si(001) surface to interact with the buckled-down Si atom at temperatures from 100 K to 300 K, and then the O-H bond of CH3OH((ads)) breaks within 10 picoseconds only at 300 K due to the elongation of the O-H bond. Furthermore, the time-resolved vibrational spectrum constructed by a wavelet transform of the structural coordinate auto-correlation function (WT-SCAF) illustrates that the O-H stretching mode of CH3OH(ads) shifts to below 3400 cm(-1) when the H atom of the O-H bond is closer to the buckled-up Si atom of the adjacent dimers. This is due to the fact that the noticeable attractive force between the H atom of the O-H bond and the dangling bond at the buckled-up Si atom of the adjacent dimers prompts the O-H bond to break and then leads to both CH3O and H species adsorbed on the buckled-down and buckled-up Si atoms, respectively.