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Master's Dissertation
DOI
https://doi.org/10.11606/D.43.2007.tde-23042008-215856
Document
Author
Full name
Henrique Santos Guidi
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2007
Supervisor
Committee
Oliveira, Mario Jose de (President)
Henriques, Vera Bohomoletz
Koning, Maurice de
Title in Portuguese
Estudo do resfriamento em um sistema com múltiplos estados fundamentais
Keywords in Portuguese
Algoritmo de Metropolis
Estados Metaestáveis
Transições de fase
Vidros
Abstract in Portuguese
Estudamos um sistema de dois níveis acoplados como um modelo que imita o comportamento de líquidos super-resfriados. Em equilíbrio o modelo apresenta uma fase líquida e uma fase cristalina com diversos estados fundamentais. O modelo é definido numa rede quadrada e a cada sítio é associada uma variável estocástica de Ising. A característica que torna este modelo particularmente interessante é que ele apresenta estados metaestáveis duráveis que podem desaparecer dentro do tempo acessível para as simulações numéricas. Para imitar o processo de formação dos vidros, realizamos simulações de Monte Carlo a taxas de resfriamento constante. Apresentamos também simulações para resfriamentos súbitos a temperatura abaixo da temperatura de fusão.
Title in English
A study of cooling in a system with several ground states.
Keywords in English
Glasses
Metastable states.
Metropolis algorithm
Phase transition
Abstract in English
We study a coupled two level systems as a model that imitate the behavior of supercooled liquids that become structural glasses under cooling. In the equilibrium the model shows a liquid phase and a crystalline phase with many grouond states. The model is defined on a square lattice and to each site a stochastic Ising variable is associated. The feature that makes this model particularly interesting is that it display durable metastables states which can vanish within the time available for numerical simulations. In order to imitate the glass former process, we perform Monte Carlo simulations at constant cooling rate. We present also simulations for quenchs to temperatures below the melting temperature.
 
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Publishing Date
2008-05-09
 
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