Abstract: The hydrogen transfer, abstraction and exchange reactions for hydrogen-rich compounds are of considerable importance in environmental and hydrogen energy chemistry. Interest in acetylene–vinylidene isomerization is long-standing,1-3 which is a benchmark for the study of hydrogen migration. The lifetime of vinylidene was long accepted as being very short, however, in 1998, a very long lifetime of at least 3.5 microseconds was claimed.2 We report the first full-dimensional quantum-mechanical calculations on the isomerization of acetylene to vinylidene on an ab initio potential energy surface. Our theoretical scheme is a combination of several methods. The Jacobi coordinates are chosen and a kind of complex absorbing potential is used to deal with the isomerization behaviour of vinylidene, which is made possible by a novel reaction coordinate defined by us. Phase space optimization in combination with physical considerations3 is used to obtain an efficient radial discrete variable representation, whereas a basis contraction scheme is applied for angular coordinates; The preconditioned inexact spectral transform method combined with an efficient preconditioner is employed to compute complex eigenstates within a desired spectral window. Our computation is very efficient, and the computed state-specific lifetimes of vinylidene will be reported and discussed in terms of experimental divergences and isomerization mechanism.
The abstraction reaction of H+SiH4 plays a significant role in chemical vapor deposition processes used in semiconductor industry, and the competition between hydrogen abstraction and exchange in this system is typical. We constructed an accurate global 12-dimensional ab initio potential energy surface,4 which describes both the H+SiH4 abstraction and exchange reactions, and performed further dynamical calculations. Our QCT calculations reveal interesting features of detailed dynamical quantities and underlying new reaction mechanisms. We designate new mechanisms for exchange found by us as torsion-tilt and side-inversion. The abstraction reaction is shown to be a combination of rebound and stripping. Results and findings from our recent dynamical studies will be reported, which are important for acquiring a deeper understanding of polyatomic abstraction and exchange reactions.