The reaction dynamics for C–Br bond breaking within BrH2C–CºCH(ads) adsorbed on Ag(111) surface has been investigated by combining density functional theory-based molecular dynamics (DFTMD) simulations with short-time Fourier transform (STFT) analysis of the dipole moment autocorrelation function. Firstly, the initial perpendicular orientation of adsorbed BrH2C–CºCH(ads) with a stronger C–Br bond will undergo dynamic rotation leading to the final parallel orientation of BrH2C–CºCH(ads) to cause the C–Br bond breaking, namely, an indirect dissociation pathway. Secondly, the initial parallel orientation of adsorbed BrH2C–CºC(ads) with a weaker C–Br bond will directly cause the C–Br scission within BrH2C–CºCH(ads), namely, a direct dissociation. To further investigate the evolution of different vibrational modes of BrH2C–CºCH(ads) along these two reaction pathways, the STFT analysis is performed to illustrate that the infrared (IR) active peaks of BrH2C–CºCH(ads) such as vCH2 [2956 cm-1(s) and 3020 cm-1(as)], vºCH (3320 cm-1) and vCºC (2150 cm-1) gradually vanish as the rupture of C–Br bond occurs and then the resulting IR active peaks such as C=C=C (1812 cm-1), w-CH2 (780 cm-1) and d-CH (894 cm-1) appear due to the formation of H2C=C=CH(ads) which are in a good agreement with experimental reflection adsorption infrared spectrum (RAIRS) at temperatures of 110 and 200 K, respectively.
