Título:	Transições de fase líquido-líquido : modelo de campo médio com duas estruturas
Autor(es):	Farias, Maria Licia de Lima
Orientador(es):	Barbosa, Marco Aurélio Alves
Assunto:	Anomalias da água Água - propriedades Teoria de campos
Data de publicação:	9-Jan-2020
Data de defesa:	29-Mai-2019
Referência:	FARIAS, Maria Licia de Lima. Transições de fase líquido-líquido: modelo de campo médio com duas estruturas. 2019. xi, 70 f., il. Dissertação (Mestrado em Ciências de Materiais)–Universidade de Brasília, Brasília, 2019.
Abstract:	A thermodynamically hypothesis for explaining the anomalous behavior of water in the supercooled and in the stable liquid region was developed in 1992 by Poole et al. The authors suggested that the sharp increase of response functions are mainly associated with the coexistence of two liquid aqueous phases namely low-density liquid (LDL) and high-density liquid (HDL). The liquidliquid phase transition (LLPT) between these two states would end on a liquid-liquid critical point (LLCP) hidden in a experimentally inaccessible area. An hypothesis that is consistent with a view that considers water as a mixture of two distinct structures, being one of the most promissing scenarios for clarifying the anomalous properties of water. Based on this concept, several of the so-called two structure equation of state (TSEOS) were proposed in order to investigate the possibility of a LLCP and the thermodynamic anomalies in supercooled water. One of the most recent models is the equation of state proposed by Holten and Anisimov which is able to describe most of the available experimental data for supercooled water. The success of the two structure approach lead us to ask for the statistical mechanical origin of this kind of equation, thus providing a connection between microscopic system details and the macroscopic behavior usually called as anomalous. This kind of question allowed us to contribute to the understanding of macroscopic behavior considered anomalous in the context of liquid water. We went over a redefinition of the coefficient of thermal expansion and a generalization of the concept of density anomaly for physical systems other than water. In this work we propose an analogy between a fluid, through the approach of compressible cell models (CC) and, a ferromagnet based on the two states description of spin-1/2. We directly compare the liquid-liquid phase transition of a fluid with the paramagnetic-ferromagnetic phase transition using the classical Bragg-Williams mean-field approximation. This framework is used to understand the liquid-liquid phase transition and its relation with waterlike density anomalies and, particularly, the density increase with temperature between 0oC and 4oC . Moreover, we also investigate the behavior of thermodynamic response functions, mainly the coefficient of thermal expansion, isothermal compressibility and heat capacity, correlating its behavior to state transitions in the case of non-interacting models and to phase transitions in systems with interaction.
Unidade Acadêmica:	Faculdade UnB Planaltina (FUP)
Informações adicionais:	Dissertação (mestrado)–Universidade de Brasília, Faculdade UnB de Planaltina, Programa de Pós-Graduação em Ciências de Materiais, 2019.
Programa de pós-graduação:	Programa de Pós-Graduação em Ciências de Materiais
Licença:	A concessão da licença deste item refere-se ao termo de autorização impresso assinado pelo autor com as seguintes condições: Na qualidade de titular dos direitos de autor da publicação, autorizo a Universidade de Brasília e o IBICT a disponibilizar por meio dos sites www.bce.unb.br, www.ibict.br, http://hercules.vtls.com/cgi-bin/ndltd/chameleon?lng=pt&skin=ndltd sem ressarcimento dos direitos autorais, de acordo com a Lei nº 9610/98, o texto integral da obra disponibilizada, conforme permissões assinaladas, para fins de leitura, impressão e/ou download, a título de divulgação da produção científica brasileira, a partir desta data.
Agência financiadora:	Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).
Aparece nas coleções:	Teses, dissertações e produtos pós-doutorado

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