University of Extremadura

About: University of Extremadura is a education organization based out in Badajoz, Spain. It is known for research contribution in the topics: Population & Hyperspectral imaging. The organization has 7856 authors who have published 18299 publications receiving 396126 citations. The organization is also known as: Universidad de Extremadura.

Dual-Level Reaction-Path Dynamics (the /// Approach to VTST with Semiclassical Tunneling). Application to OH + NH3 .fwdarw. H2O + NH2

Abstract: We consider a new approach to reaction-path dynamics calculations in which the reaction path is calculated at a low level (LL) of theory and stationary point information from a high level (HL) of theory is used to interpolate corrections to energetic quantities, vibrational frequencies, and moments of inertia. Such a calculation is labeled XII/Y, where X denotes the high level and Y the low level. The theory is applied to the reaction OH + NH[sub 3] and three isotopomeric analogs. The highest-level optimization reported for the saddle point is QCISD(T)//MP2/aug-cc-pVTZ, which yields a classical barrier height of 3.65 kcal/mol. The rate constant is calculated at two levels, QCISD(T)//MP2/aug-cc-p VTZ[MP2/aug-cc-p VDZ] ///MP2/6-31G** and QCISD(T)//MP2/aug-cc-pVTZ[MP2/aug-cc-pVDZ] ///PM3-SRP; the calculated rare constant for the unsubstituted reaction is approximately invariant to the low level used in the dual-level scheme and agrees with experiment within a factor of 1.13 at 250 K and within a factor of 1.14 at 1500 K. 79 refs., 4 figs., 13 tabs.