Complex molecules often have many structures (conformations) of the reactants and the transition states, and these structures may be connected by coupled-mode torsions and pseudorotations; some but not all structures may have hydrogen bonds in the transition state or reagents. A quantitative theory of the reaction rates of complex molecules must take account of these structures, their coupled-m...

Variational Transition State Theory with Multidimensional Tunneling (VTST/MT) has been successfully used for calculating rate constants of reactions in gas and condensed phases. The current software implementation of VTST/MT is, however, based on the assumption of a fast, serial evaluation of the energetic information of a given molecular structure. We propose a simple and effective parallel me...

We present a new formulation of variational transition state theory (VTST) called multi-structural VTST (MS-VTST) and the use of this to calculate the rate constant for the 1,4-hydrogen shift isomerization reaction of 1-pentyl radical and that for the reverse reaction. MS-VTST uses a multifaceted dividing surface and provides a convenient way to include the contributions of many structures (typ...

Multi-path variational transition state theory (MP-VTST) provides a conformationally complete framework for calculating gas-phase rate constants. For reactions in which the transition state has distinguishable torsional minima (which include most reactions), there are multiple possible reaction paths. In principle MP-VTST includes the contributions from all the reaction paths, and it should exp...

Transition state theory (TST) 1 is the most widely used theory for calculating rates of bimolecular eactions occurring in the gas phase and in condensed phases. TST is also incorporated into the widely used RRKM theory for unimolecular reactions. The popularity of TST is largely due to its simplicity and its usefulness for correlating trends in reaction rates in terms of easily interpreted quan...

The ring-polymer molecular dynamics (RPMD) was used to calculate the thermal rate coefficients of two-channel roaming reaction H + MgH. Both channels, tight and roaming, are explicitly considered. This is a pioneering attempt exerting RPMD method multi-channel reactions. With help newly developed optimization-interpolation protocol for preparing initial structures adaptive choosing force consta...

In this work, we investigate the possibility of describing gas phase atomic cluster dissociation by means of variational transition state theory (vTST) in the microcanonical ensemble. A particular emphasis is placed on benchmarking the accuracy of vTST in predicting the dissociation rate and kinetic energy release of a fragmentation event as a function of the cluster size and internal energy. T...

In this work, an improved approach for computing cluster dissociation rates using Monte Carlo (MC) simulations is proposed and a discussion is provided on its applicability as a function of environmental variables (e.g., temperature). With an analytical transformation of the integrals required to compute variational transition state theory (vTST) dissociation rates, MC estimates of the expectat...

In variational transition-state theory (VTST) and semiclassical tunnelling calculations, especially those with semiempirical potential-energy surfaces, it is sometimes desirable to match the classical energies and vibration frequencies of some points (eg . the reactant, saddle point, product, van der Waals complex, ion-molecule complex) along the minimum-energy path (MEP) and in the reaction sw...