Quantum Mechanical Calculations
Mostrando 13-24 de 37 artigos, teses e dissertações.
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13. Avaliação in silico de inserções com boro em moléculas com atividade farmacológica
The growth of leukemia incidence, cardiac problems and global AIDS epidemic, with appearing of resistant forms of HIV, stimulated the search of new medications. In this work, we investigated new active pharmacologic compounds based on boron including the anti-HIV drugs. The interest in boron compounds with pharmacologic activity has increased in recent years
Publicado em: 2006
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14. The density of states and band gap of liquid water by sequential Monte Carlo/Quantum mechanics calculations
Electronic properties of liquid water were investigated by sequential Monte Carlo/Quantum mechanics calculations. The density of states (DOS) and HOMO-LUMO gap (E G) of liquid water have been determined by Hartree-Fock and Density Functional Theory (DFT) calculations. The quantum mechanical calculations were carried out over uncorrelated supermolecular struc
Brazilian Journal of Physics. Publicado em: 2004-03
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15. Determinação da estrutura molecular do ciclooctano por métodos ab initio e difração de elétrons na fase gasosa
The determination of the molecular structure of molecules is of fundamental importance in chemistry. X-rays and electron diffraction methods constitute in important tools for the elucidation of the molecular structure of systems in the solid state and gas phase, respectively. The use of quantum mechanical molecular orbital ab initio methods offer an alternat
Química Nova. Publicado em: 2000-10
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16. Modelamento mecanico-quantico de tensores polares
Experimental polar tensors for the CH2Cl2, CF2Cl2, CF3Cl, CFCl3, CH3F, CH3Cl, CH3I, Cl2CO, F2CO, Cl2CS and F2CS molecules were determined with the aim of testing previously established electronegativity models for tensor invariants estimation. The method of determination uses comparison of the several possible sets of polar tensors for a molecule (correspond
Publicado em: 1994
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17. Close agreement between the orientation dependence of hydrogen bonds observed in protein structures and quantum mechanical calculations
Hydrogen bonding is a key contributor to the exquisite specificity of the interactions within and between biological macromolecules, and hence accurate modeling of such interactions requires an accurate description of hydrogen bonding energetics. Here we investigate the orientation and distance dependence of hydrogen bonding energetics by combining two quite
National Academy of Sciences.
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18. Quantum-mechanical calculations of the stabilities of fluxional isomers of C4H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{7}^{+}}}\end{equation*}\end{document} in solution
Although numerous quantum calculations have been made over the years of the stabilities of the fluxional isomers of C4H\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{7}
The National Academy of Sciences.
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19. Vacuum ultraviolet circular dichroism as an indicator of helical handedness in nucleic acids.
Calculated circular dichroism spectra are presented for double-stranded polynucleotides of regular sequences in A-RNA, A-DNA, B-DNA, and Z-DNA conformations. Quantum mechanical matrix method calculations were carried out in the near and vacuum ultraviolet regions. In the near UV, the calculated spectra agreed qualitatively with the measured spectra. However
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20. Barrier Height for the Exchange Reaction F + HF → FH + F
There exists a body of conflicting data as to the existence or nonexistence of FHF, ClHCl, BrHBr, and IHI as chemically bound molecular species. Ab initio quantum mechanical electronic structure calculations are presented which predict linear symmetric FHF to be unstable. The barrier height for the F + HF exchange reaction is suggested to be no less than 18
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21. Keeping Mars warm with new super greenhouse gases
Our selection of new super greenhouse gases to fill a putative “window” in a future Martian atmosphere relies on quantum-mechanical calculations. Our study indicates that if Mars could somehow acquire an Earth-like atmospheric composition and surface pressure, then an Earth-like temperature could be sustained by a mixture of five to seven fluorine c
The National Academy of Sciences.
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22. Discrete wave mechanics: The hydrogen atom
The quantum mechanical problem of the hydrogen atom is treated by use of a finite difference equation in place of Schrödinger's differential equation. The exact solution leads to a wave vector energy expression that is readily converted to the Bohr-Rydberg formula. (The calculations here reported are limited to spherically symmetric states.) The wave vector
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23. Mechanism for antibody catalysis of the oxidation of water by singlet dioxygen
Wentworth et al. [Wentworth, P., Jones, L. H., Wentworth, A. D., Zhu, X. Y., Larsen, N. A., Wilson, I. A., Xu, X., Goddard, W. A., Janda, K. D., Eschenmoser, A. & Lerner, R. A. (2001) Science 293, 1806–1811] recently reported the surprising result that antibodies and T cell receptors efficiently catalyze the conversion of molecular singlet oxygen (1O2) plu
The National Academy of Sciences.
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24. RESONANCE STABILIZATION OF CYCLE GROUPS OF HYDROGEN-BONDED WATER MOLECULES
A quantum-mechanical resonance effect can be associated with cyclic groups of hydrogen-bonded water molecules and, conceivably, might influence the structure of liquid water (M. Ageno, these PROCEEDINGS, 57, 567 (1967)). However, from the calculations presented here, this resonance stabilization appears to be too small (<0.1 kcal/mole) to over come the therm