نتایج جستجو برای: valence bond theory

تعداد نتایج: 859522  

2001
Emily A. CARTER

A scheme is presented for calculating the heats of formation of adsorbed species on metal surfaces using only two pieces of gas phase data, both of which are available from either theory or experiment. Using this quasiempirical valence bond (QVB) approach, heats of adsorption and adsorbate-surface bond strengths can be estimated, yielding predictions of surface thermochemistry and reaction mech...

1998
Wei Wu Shi-jun Zhong Sason Shaik

Ž . Ž . A semi-empirical valence bond VB method, called VBDFT s , is described and applied to C H conjugated n nq2 hydrocarbons. The method is a Huckel-type VB scheme with energies scaled to density functional theory energies based on a ̈ single parameter; the matrix element l due to spin transposition between bonded atoms. Total energies, excitation energies, resonance and p-bond energies are p...

2017
Anna Miglio Christophe P Heinrich Wolfgang Tremel Geoffroy Hautier Wolfgang G Zeier

Quaternary chalcopyrites have shown to exhibit tunable band gaps with changing anion composition. Inspired by these observations, the underlying structural and electronic considerations are investigated using a combination of experimentally obtained structural data, molecular orbital considerations, and density functional theory. Within the solid solution Cu2ZnGeS4-x Se x , the anion bond alter...

2001
William A. Goddard Arthur Amos Noyes

Ab initio calculations (Hartree-Fock, generalized valence bond, and configuration interaction), utilizing relativistic core potentials, have been used to follow the oxidative addition of Hz to Pt(PH,),. We find an activation barrier of 2.3 kcal/mol and an exothermicity of 15.9 kcal/mol. From examination of the geometries and wave functions, we find that up to the transition state the H-H bond i...

2017
Srikanth Madala Kathryn Hausbeck

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Journal: :Journal of chemical theory and computation 2009
Lingchun Song Yirong Mo Jiali Gao

An effective Hamiltonian mixed molecular orbital and valence bond (EH-MOVB) method is described to obtain an accurate potential energy surface for chemical reactions. Building upon previous results on the construction of diabatic and adiabatic potential surfaces using ab initio MOVB theory, we introduce a diabatic-coupling scaling factor to uniformly scale the ab initio off-diagonal matrix elem...

Journal: :Inorganic chemistry 2003
Zhaohui Li Alicia M Beatty Thomas P Fehlner

Utilization of binary information encoded in the charge configuration of quantum-dot cells (the quantum-dot cellular automata, QCA, paradigm) requires molecule-sized dots for room temperature operation. Molecular QCA cells are mixed-valence complexes, and the evaluation and functionalization of an unsymmetrical heterobinuclear, two-dot, Fe-Ru molecular QCA cell is described. The solid state str...

2007
Young-Han Shin Jong-Yeog Son Byeong-Joo Lee Ilya Grinberg Andrew M Rappe

We report the displacive and order–disorder characters of PbTiO3 analyzed using a classical atomic model which was developed under the inverse relation between the bond length and the bond valence. The ferroelectric phase changes to the paraelectric phase around 700 K, and the histograms of Ti–O and Pb–O bond lengths have three peaks which become a single peak above the phase transition tempera...

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