Scaling of Transition State Vibrational Frequencies and Application of d-Band Theory to the Brønsted–Evans–Polanyi Relationship on Surfaces

2021 ◽  
Author(s):  
Joshua L. Lansford ◽  
Sophia J. Kurdziel ◽  
Dionisios G. Vlachos
Keyword(s):  
Transition State ◽  
Vibrational Frequencies ◽  
Band Theory

Transition state dynamics and a QM/MM model for the Cl– + C2H5Cl SN2 reaction

2004 ◽  
Vol 82 (6) ◽  
pp. 891-899 ◽  
Author(s):  
Lipeng Sun ◽  
Eunkyung Chang ◽  
Kihyung Song ◽  
William L Hase
Keyword(s):  
Hydrogen Atom ◽  
Transition State ◽  
Reaction Dynamics ◽  
Vibrational Frequencies ◽  
Dynamics Simulation ◽  
Rrkm Theory ◽  
Direct Dynamics ◽  
Sn2 Reaction ◽  
Classical Trajectories ◽  
Link Atom

A MP2/6-31G* direct dynamics simulation is used to study the dynamics of the central barrier [Cl-C2H5-Cl]– for the Cl– + C2H5 SN2 reaction. The majority of the trajectories move off the central barrier to form the Cl––C2H5Cl complex and appear to undergo efficient IVR as assumed by RRKM theory. However, some of the trajectories move directly to products without forming the complex, a non-RRKM result. A hydrogen atom link-atom QM/MM model is described for studying the dynamics of [X-CH2R-Y]– central barriers with the -R substituent. The model is used to calculate vibrational frequencies for the [Cl-C2H5-Cl]– central barrier.Key words: SN2 reaction dynamics, RRKM theory, QM/MM model, central barrier dynamics, direct dynamics classical trajectories.

Transition state structure, barrier height, and vibrational frequencies for the reaction Cl+CH4→CH3+HCl

1989 ◽  
Vol 90 (12) ◽  
pp. 7137-7142 ◽  
Author(s):  
Thanh N. Truong ◽  
Donald G. Truhlar ◽  
Kim K. Baldridge ◽  
Mark S. Gordon ◽  
Rozeanne Steckler
Keyword(s):  
Transition State ◽  
Barrier Height ◽  
Vibrational Frequencies ◽  
State Structure ◽  
Transition State Structure

On the structure of S42+ and its formation from 2S2+•Ab initio SCF and CASSCF studies

1994 ◽  
Vol 72 (2) ◽  
pp. 298-303 ◽  
Author(s):  
Mousumi Sannigrahi ◽  
Friedrich Grein
Keyword(s):  
Transition State ◽  
Ab Initio ◽  
Minimum Energy ◽  
Vibrational Frequencies ◽  
Square Planar ◽  
Experimental Values ◽  
Minimum Energy Paths

Ab initio studies up to the MP2/6-31G* level were performed on the geometry and energy of S42+. Eleven different structures were considered. In the RHF/6-31G* method, the square structure is the most stable, followed by the trans-planar C2h structure. S42+ (square) is 105.9 kcal/mol less stable than 2S22+. Minimum energy paths were calculated for the reaction 2S2+ → S42+, both in C2v and D2h symmetry. Using RHF/6-31G*, the transition state lies about 50 kcal/mol above the energy of square planar S42+. Using CASSCF or MP2 methods this energy can be significantly lowered (to about 33 kcal/mol in MP2/6-31G*). Calculated vibrational frequencies for the square structure are also given and compared with experimental values.

Ab initio band theory approach to electron energy loss near edge structures

1988 ◽  
Vol 46 ◽  
pp. 506-507
Author(s):  
Xudong Weng ◽  
O.F. Sankey ◽  
Peter Rez
Keyword(s):  
Ab Initio ◽  
Local Density ◽  
Interpolation Method ◽  
Atomic Orbital ◽  
Plane Waves ◽  
Large Set ◽  
Theory Approach ◽  
Band Theory ◽  
Atomic Orbitals ◽  
Pseudopotential Calculations

Single electron band structure techniques have been applied successfully to the interpretation of the near edge structures of metals and other materials. Among various band theories, the linear combination of atomic orbital (LCAO) method is especially simple and interpretable. The commonly used empirical LCAO method is mainly an interpolation method, where the energies and wave functions of atomic orbitals are adjusted in order to fit experimental or more accurately determined electron states. To achieve better accuracy, the size of calculation has to be expanded, for example, to include excited states and more-distant-neighboring atoms. This tends to sacrifice the simplicity and interpretability of the method.In this paper. we adopt an ab initio scheme which incorporates the conceptual advantage of the LCAO method with the accuracy of ab initio pseudopotential calculations. The so called pscudo-atomic-orbitals (PAO's), computed from a free atom within the local-density approximation and the pseudopotential approximation, are used as the basis of expansion, replacing the usually very large set of plane waves in the conventional pseudopotential method. These PAO's however, do not consist of a rigorously complete set of orthonormal states.

Memapsin 2, a drug target for Alzheimer's disease

2003 ◽  
Vol 70 ◽  
pp. 213-220 ◽  
Author(s):  
Gerald Koelsch ◽  
Robert T. Turner ◽  
Lin Hong ◽  
Arun K. Ghosh ◽  
Jordan Tang
Keyword(s):  
Crystal Structure ◽  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Transition State ◽  
Amyloid Precursor Protein ◽  
Therapeutic Target ◽  
Drug Target ◽  
Aspartic Protease ◽  
Precursor Protein ◽  
Memapsin 2

Mempasin 2, a ϐ-secretase, is the membrane-anchored aspartic protease that initiates the cleavage of amyloid precursor protein leading to the production of ϐ-amyloid and the onset of Alzheimer's disease. Thus memapsin 2 is a major therapeutic target for the development of inhibitor drugs for the disease. Many biochemical tools, such as the specificity and crystal structure, have been established and have led to the design of potent and relatively small transition-state inhibitors. Although developing a clinically viable mempasin 2 inhibitor remains challenging, progress to date renders hope that memapsin 2 inhibitors may ultimately be useful for therapeutic reduction of ϐ-amyloid.

Collisional dynamics of Ca1D + HBr reactions: evidence for transition-state motions

1999 ◽  
Vol 97 (8) ◽  
pp. 967-976 ◽  
Author(s):  
M. Garay Salazar, J. M. Orea Rocha, A.
Keyword(s):  
Transition State ◽  
Collisional Dynamics
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