Variational transition-state theory and semiclassical tunnelling calculations with interpolated corrections: a new approach to interfacing electronic structure theory and dynamics for organic reactions

Abstract

MN 55455443 1, USAIn 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 ( e g . the reactant, saddle point, product, van der Waals complex, ion-molecule complex) along the minimum-energy path (MEP) and in the reaction swath with high-level results, as this can improve the accuracy. This can be accomplished by adding a correction function to the calculated energies or frequencies. In this paper, we introduce a three-point or zero-order interpolated correction method which is based on the correction at three points, in particular the saddle point and two stationary points, one on each side of the MEP. We use the corrections at these points to build a correction function for the classical energy and for each vibrational mode frequency along the MEP. The function is calibrated such that the corrected result matches the accurate values at these stationary points. The functional forms to be used depend on the shape of the MEP under consideration and the relative correction values at those points. Similar treatments are applied to the determinant of the moment of inertia tensor along the reaction path and to the potential-energy function in non-adiabatic regions of corner-cutting tunnelling paths. Once parameters in the functional forms are determined, we then use the corrected energy, frequency and moments of inertia information together with other MEP and reaction swath data, as obtained directly from the potential-energy surface, to perform new VTST calculations. Details of the implementation are presented, and applications to reaction rate calculations of the OH + CH, -+ H, O + CH, and CF, + CD, H --+ CF, H + CD, reactions are included.

Gold‐Catalyzed Cross‐Coupling Reactions: An Overview of Design Strategies, Mechanistic Studies, and Applications

“…Mechanistic studies indicatedt hat the reductivee limination occurred in ac oncerted manner,a nd ap rior phosphine dissociation step was not necessary.C ontraryt ot he previouss tudies on dialkylgold(III) complexes, the addition of phosphine ligands to the Au III complex accelerated the reductive elimination. Direct dynamics calculations that incorporate as mall curvature multi-dimensional tunneling [315][316][317] Calculated activation barriers for unimolecular CÀCb ond reductive elimination from as eries of square-planar Au III complexes of the form cis-[R 1 R 2 Au(PPh 3 )Cl] (R 1 ,R 2 = H, alkyl, aryl, and vinyl groups) depended on the hybridization of bondforming C, electron-donating/withdrawing groups on the arene ligand,a nd AuÀCb ond strength in the ground and TS geometries. Further,f acile concerted biaryl formation has been demonstrated from as eries of bimetallic, Au II -Au II complexes at low temperature.…”

A product branching ratio controlled by vibrational adiabaticity and variational effects: Kinetics of the H + trans-N2H2 reactions

“…20-23) and 4.1 and −37.5 kcal/mol. 24 The potential energy surfaces used in these rate calculations are not reliably accurate, and dual-level direct dynamics 22,25 was employed 22 to try to improve the accuracy. We will show that the description of these reactions will be qualitatively different when we use a higher-quality potential energy surface.…”

Ping‐Pong Tunneling Reactions: Can Fluoride Jump at Absolute Zero?

“…[64] The rate constants were computed with Polyrate17 [65] using Gauss-rate17B [66] as an interface between Polyrate and the Gaussian16 program suite. Semi-classical rates were computed with the canonical variational transition-state theory (CVT), [67] and small curvature tunneling (SCT) was used for the tunneling correction [68,69] with a step size of 0.001 Bohr and including quantized reactant state tunneling (QRST) [70] for the reaction coordinate mode (see the Supporting Information for aPolyrate input file example).…”