Phase transitions through a metastable intermediate state
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StatusThe thesis was presented on the 7 October, 2015Approved by NCAA on the 19 November, 2015 Abstract – 1.38 Mb / in romanianThesisCZU [532.78+531.19](043.2)
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Keywords
supercooled liquid, phase transitions, mean transition time, cluster, heterogeneous system, bifurcation, parametrical model, stability analysis, metastable states, complex systemSummary
The thesis consists of introduction, three chapters, general conclusions and recommendations, and bibliography of 104 references. This work contains 41 figures, one table and is carried on 134 pages. The results are published in 20 research papers.
Field of study: physics of complex systems
The goal of the research was to study first-order phase transitions in a supercooled liquid in the presence of an intermediate metastable state.
The objectives were to develop an advanced theory of first order phase transitions in a supercooled liquid based on the cluster concept, bifurcation and stability analysis for the phase transition in the presence of an intermediate metastable state in the model with one and two order parameters, estimation of the intermediate state’s role in the kinetics of transitions induced by fluctuations from the initial to the final states, analysis of the impact of heterogeneity and external field on the phase transition and determination of the control parameters values accordingly to the experimental data, as well as determination of the general properties of stochastic mathematical model which describes the interaction of agents in a heterogeneous system.
Scientific novelty consists in the introduction of a generalized parametric model based on Landau-type kinetic potential with order parameters and control parameters, being shown the importance of the heterogeneity, external field and intermediate metastable state on the first order phase transition acceleration and, therefore, transition time reduction. General properties of the mathematical model, which describes stochastic interaction of agents in the heterogeneous system by computation-probabilistic modeling based on the formula for distribution of agents in clusters, were determined for the first time.
The scientific problem solved concerns the development of the theory of first order phase transitions based on the intermediate metastable state and the cluster concept for analytic and numerical modeling of the relaxation processes in supercooled liquids and protein solutions in the process of crystallization, as well as the determination of a general solutions and mathematical properties of theoretical models applied to the study of phase transitions.
The theoretical significance is to develop the theory of first order phase transitions in supercooled liquid by taking into account the system heterogeneity due to the presence of clusters and the influence of constant and periodic external fields.
Applicative value of the work is determined by the importance of understanding the connection between the properties, microscopic structure of the substance and macroscopic conditions of material processing, which is of great importance in the production of new materials with advanced technological properties.
Results implementation: the results are used within the institutional project of fundamental scientific research 15.817.02.29F, strategic direction “Materials, technologies and innovative products”, within the master courses curricula “The physics of clusters”, “Complex systems modeling” and “The theory of crystallization processes” held at the Moldova State University.
Oficial Reviewers
- Ion Geru
doctor habilitat, professor, Institute of the Electronic Engineering and Nanotechnologies - EREMEEV Vitalie
doctor în ştiinţe fizico-matematice, conferențiar cercetător, Universidad Diego Portales, Santiago de Chile
Council's Members
- Mihai Vladimir, president
doctor habilitat, professor - Denis Nica , secretary
doctor habilitat, professor, Moldova State University - Nicolae Enache, member
doctor habilitat, professor, Institute of Applied Physics of the - Vasile Tronciu, member
doctor habilitat, professor - Nicolae Balmuş, member
doctor, associate professor (docent), Chisinau Pedagogical State University "Ion Creanga" - Aurelia Prepeliţă , member
doctor, associate professor (docent), Moldova State University
Theses
