Monte Carlo method using AB initio total energy calculation

Author(s)

Luana Sucupira Pedroza

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Física (IF/SBI)
• Defense date: 2006-08-24

Examining board members

Antonio Jose Roque da Silva; Rodrigo Barbosa Capaz; Maria Cristina dos Santos

• Advisor: Antonio Jose Roque da Silva

Abstract

Computer simulations are essential tools to the research of physical systems at finite temperatures. Monte Carlo (MC) and Molecular Dynamics (MD) methods are the major techniques used for this purpose, and empirical potentials are traditionally employed in these simulations. These potentials, however, are built to describe with precision the system near some region of its configuration space, thus there is no guarantee that they will provide reliable results in other instances. Therefore, there is a great interest in the combination of MC and MD simulations with methods that describe the electronic structure with high precision (ab initio methods). In this work we have developed a MC program where the total configurational energies are obtained via Density Functional Theory (DFT). As an initial application of our methodology we have studied a silicon cluster (Si5). In these simulations we have investigated the structural properties of these cluster at diferent temperatures and estimated the melting temperature. Furthermore, we also propose a new formulation for water simulations,where we combine the ab initio MC with intramolecular geometry optimizations. As an illustration of our methodology, we show the results for the water dimer simulations. This system is a prototype of the hydrogen bond where we already have both intra and intermolecular bonds. (AU)