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Identifier

uch.physics.phd//1991DIS0163

Title

2-Dimensional structures in a triangular lattice with a nonlinear substrate

Alternative Title

Διδιάστατες δομές σε τριγωνικό πλέγμα με μη-γραμμικό υπόστρωμα

Author

Βλαστού-Τσιγκάνου, Γεωργία Α

Thesis advisor

Φλυτζάνης, Νικόλαος

Abstract

A detailed study is performed of a model on a triangular lattice, which can contribute to the interpretation of the modulated phases encountered in solids. The important element of the model is the competing mechanism between neighbouring harmonic forces and the on-site nonlinear Φ4 potential. As a result of this competition, stable commensurate structures appear in the phase diagram, either with short or long period. Discommensurations and even incommensurate phases rise in the form of "devil's staircases". Also domain walls and triangular wall formations were found metastable and their detailed study gives significant information about the existence of related structures. The problem is treated classically and semi-quantum mechanichally using an independent site approximation and a quantum variational "ansatz". Minimization of the potential energy and the Helmholz free energy is achieved by the simulated annealing Monte Calro method. A specific application and extention of the model is done on LiIO3. Using 2-degrees of freedom on a hexagonal lattice, we have been able to explain the transition temperature between two of its phases

Language

English

Issue date

1991-02-01

Date available

1997-06-6

Collection

School/Department--School of Sciences and Engineering--Department of Physics--Doctoral theses

Type of Work--Doctoral theses

Permanent Link

https://elocus.lib.uoc.gr//dlib/c/f/e/metadata-dlib-1991DIS0163.tkl