Development of a restricted simplex for optimizing force constants in normal coordinate calculations and applications to SERS spectra.
Item
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Title
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Development of a restricted simplex for optimizing force constants in normal coordinate calculations and applications to SERS spectra.
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Identifier
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AAI9605676
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identifier
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9605676
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Creator
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Vivoni, Alberto L.
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Contributor
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Co-Advisers: Ronald L. Birke | John R. Lombardi
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Date
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1995
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Physical
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Abstract
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A restricted simplex method was developed to optimize force constants in normal coordinate calculations. The method keeps the normal modes from crossing over each other by requiring that the normal mode assignments are obeyed during iterations. A description of the method and results of pyrimidine, aniline and flavin calculations are presented. The method is compared with other methods of obtaining force constant values and evaluated on the basis of frequency and isotopic shift match and the reasonableness of the calculated force constants. The method was applied to the SERS spectra of ammonia, pyridine, adenine and NAD{dollar}\sp+{dollar}. The frequency shifts between the solution and SERS spectra were reproduced by perturbing the force field obtained from solution calculations. The accuracy of the calculation method allowed one to obtain information about the interaction between the molecule and the surface such as orientation of the molecule on the surface, charge re-distribution and structural changes. The method was also applied to 4-atoms clusters. Quantum mechanical calculations of rhomboidal Si4 were reproduced and the force fields of tetrahedral P{dollar}\sb4{dollar}, Ta{dollar}\sb4{dollar} and Bi{dollar}\sb4{dollar} were calculated.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
