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Master's Dissertation
DOI
10.11606/D.43.2006.tde-10012007-204227
Document
Author
Full name
Rafael Carvalho Barreto
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2006
Supervisor
Committee
Canuto, Sylvio Roberto Accioly (President)
Borin, Antonio Carlos
Petrilli, Helena Maria
Title in Portuguese
"Propriedades eletrônicas de líquidos homogêneos"
Keywords in Portuguese
Estrutura Eletrônica
Mecânica Quântica
Método de Monte Carlo
Termodinâmica
Abstract in Portuguese
O estudo da polarização eletrostática em líquidos homogêneos é crucial para compreender as propriedades termodinâmicas e de solvatação. Estes efeitos de polarização são também importantes para estudar a dinâmica molecular de reações químicas, conformações (tais como proteínas), e do meio solvente (solvatocromismo e RMN). Nesta dissertação, estudou-se a variação do momento de dipolo da fase gasosa para a fase líquida das moléculas: acetona, acetonitrila, amônia e água. Os momentos de dipolo em fase gasosa foram obtidos com cálculos quânticos ab initio para a molécula isolada. Para a fase líquida, cálculos equivalentes foram feitos sobre estruturas geradas de simulação computacional clássica (Monte Carlo). Tal procedimento foi feito segundo a metodologia "Monte Carlo / Mecânica Quântica - Seqüencial". Este método foi aplicado iterativamente, tornando possível estudar a variação do momento de dipolo e das propriedades termodinâmicas devido à mútua polarização das moléculas do solvente. Usando os resultados calculados, uma discussão foi realizada sobre a polarização eletrostática e o dipolo induzido em fase líquida.
Title in English
Electronic properties of homogeneos liquids
Keywords in English
Electronic Structure
Monte Carlo Method
Quantum Mechanics
Thermodynamics
Abstract in English
The study of the electrostatic polarization in homogeneous liquids is crucial to the understanding of thermodynamic and solvation properties. These polarization effects are also important to study molecular dynamics of chemical reactions, conformations (such as proteins), and solvent environment (solvatocromism and NMR). In this dissertation, the variation of dipole moments from the gas phase to the liquid phase of acetone, acetonitrile, ammonia and water, were studied. The dipole moments in the gas phase were obtained with quantum mechanical ab initio calculation on the isolated molecule. For the liquid phase, equivalent quantum mechanical calculations were made on structures generated from classical computer simulations (Monte Carlo). Such procedure was made according to the methodology "Sequential - Monte Carlo/Quantum Mechanics". This method was applied iteratively, becoming possible to study the variation of the dipole moment and the thermodynamic properties due to the mutual polarization of the solvent molecules. Using the calculated results, a discussion was made of the electrostatic polarization and the induced dipole moment in the liquid phase.
 
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Publishing Date
2007-02-01
 
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