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Doctoral Thesis
DOI
10.11606/T.43.1996.tde-30102012-132712
Document
Author
Full name
Luiz Adolfo de Mello
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1996
Supervisor
Committee
Pessoa, Sonia Frota (President)
Assali, Lucy Vitoria Credidio
Mota, Ronaldo
Muniz, Roberto Bechara
Saxena, Rajendra Narain
Title in Portuguese
Estudo de propriedades locais em impureza intersticiais em hospedeiros metálicos.
Keywords in Portuguese
Cálculo de Estrutura Eletrônica
Comportamento Magnético
Deslocamento Isomérico.
Estudo de Propriedades Locais
Impurezas Intersticiais
Abstract in Portuguese
Neste trabalho realizamos um estudo do comportamento do momento magnético e do deslocamento isomérico de uma impureza intersticial de Fe em hospedeiros metálicos de valências 4 (Ti, Zr), 3 (Sc, Y). Investigamos também impurezas intersticiais e substitucionais de Mo e Fe em hospedeiros divalentes. Para realizar este estudo fizemos cálculos de estrutura eletrônica utilizando o RS-LMTO-ASA ("Real Space - Linear Muffin-Tin Orbital - Atomic Spherical Approximation"), um método de primeiros princípios dentro da aproximação do funcional densidade local, implementado no espaço real. Calculamos o momento magnético no sítio da impureza nos sistemas acima e constatamos que a impureza intersticial de Fe é não magnética nos hospedeiros de valências 4 e 3, e que tanto as impurezas intersticiais como as substitucionais podem apresentar momento magnético nos hospedeiros divalentes. Mostramos que para os sistemas divalentes o momento magnético depende fortemente da relaxação. Os nossos resultados são explicados através de um modelo simples, baseado no modelo de Wolff. Investigamos também o comportamento do deslocamento isomérico no sítio da impureza de Fe nesses vários sistemas. Constatamos que os nossos resultados concordam razoavelmente bem com os dados experimentais e explicam o comportamento das tendências observadas.
Title in English
Study of Local Properties in Interstitial Impurities in Metalic Hosts.
Keywords in English
Electronic Structure Calculations
Interstitial Impurities
Isomer Shift.
Magnetic Behavior
Study of Local Properties
Abstract in English
In the present work, we have studied the magnetic moments and the behavior of the isomer shift at the interstitial Fe impurity site in Ti, Sc, Zr and Y hosts. We have also investigated interstitial and substitutional Fe and Mo impurities in Ca, Sr and Yb hosts. To perform the calculations, we have used the RS-LMTO-ASA scheme, a first principles method, within the local spin density approximation, implemented in real space. We calculated the magnetic moments at the impurity site in the above systems and all the substitucional impurities are found to be magnetic. The results show that interstitial Fe is non-magnetic in the tri- and tetravalent hosts, but interstitial Fe and Mo impurities could develop local magnetic moment in divalent hosts. 'We show that the magnetic moment at the impurity site in these divalent hosts is strongly dependent on lattice relaxation. The results can be explained using simple arguments based on Wolff model. We have investigated in a systematic way the behavior of the isomer shift of Fe impurities in these systems. We observed that our results are in generally good agreement with experiment and lead to better understanding of the observed trends in terms of the volume occupied by the Fe in each host.
 
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45859MELLO.pdf (66.52 Mbytes)
Publishing Date
2012-11-01
 
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