Models for transition metal oxides and for protein design

A large number of properties of solid state materials can now be predicted with standard first-principles methods such as the Local Density (LDA) or Generalized Gradient Approximation (GGA). However, known problems exist when using these methods for predicting the electronic structure and total energy of transition metal oxides. We demonstrate that the LDA+U method, in which localized d electrons are treated with a Hubbard-like model, gives considerably better predictions in band gap, magnetization, lattice constants, redox potential, mixing energy and other properties of lithium transition-metal oxides. The systematic improvement of both electronic structure and total energy properties suggests that the more accurate treatment of electron correlation on the transition metal sites will greatly enhance the predictive character of ab-initio methods for these materials. In a even more dramatic example, the more accurate electronic and total energy descriptions with LDA+U have enabled us to study the finite temperature phase diagram of LixFePO4. It is found that an unexpected solid solution phase are mainly stabilized by the entropy contribution of localized d electrons. This brings the less visited problem of the effects of electronic correlation on thermodynamics into our attention.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Physics.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2006

Author dc:creator

• Zhou, Fei, Ph. D. Massachusetts Institute of Technology

Advisor dc:contributor.advisor

• Gerbrand Ceder and John D. Joannopoulos.

• Physics.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/39558

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/39558