Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-06-02T21:55:36Z No. of bitstreams: 1 RonielDeLimaAraujo_DISSERT.pdf: 7628198 bytes, checksum: ee3c1fe4ca93c9df76b5459cb7bea112 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-06-07T21:28:06Z (GMT) No. of bitstreams: 1 RonielDeLimaAraujo_DISSERT.pdf: 7628198 bytes, checksum: ee3c1fe4ca93c9df76b5459cb7bea112 (MD5) / Made available in DSpace on 2017-06-07T21:28:06Z (GMT). No. of bitstreams: 1 RonielDeLimaAraujo_DISSERT.pdf: 7628198 bytes, checksum: ee3c1fe4ca93c9df76b5459cb7bea112 (MD5) Previous issue date: 2017-03-17 / Neste trabalho, estudamos as propriedades estruturais, eletr?nicas, ?pticas e vibracionais dos cristais ortorr?mbicos de treonina, obtidos atrav?s de simula??es computacionais no formalismo DFT (Teoria Funcional da Densidade), nas aproxima??es de densidade local (LDA-CAPZ) e no gradiente generalizado GGA-PBE). L-treonina ? um amino?cido essencial que desempenha um papel importante nos sistemas biol?gicos, sendo o ?ltimo dos 20 amino?cidos que comp?em as prote?nas, a serem identificados. Para o cristal l-treonina, a otimiza??o da geometria cristalina, par?metros de rede, ?ngulos e dist?ncias interat?micas, estrutura de banda, densidade de ?tomo a ?tomo, absor??o ?ptica, fun??o diel?trica, ?ndice de refra??o, condutividade ?tica, fun??o de perda, espectro infravermelho e Raman. Os par?metros de rede calculados est?o pr?ximos dos resultados experimentais, foram obtidos um gap de banda E = 5,06 eV e um gap de banda E (X ? S) = 4,91 eV indiretos dentro do GGA e LDA, respectivamente. A an?lise da densidade de estados de el?trons permitiu identificar as contribui??es por ?tomo para os estados das bandas de val?ncia e de condu??o, nas propriedades ?pticas ? poss?vel observar uma sensibilidade ao plano de polariza??o da luz incidente 001. Foi obtido um bom acordo entre Os espectros vibracionais IR e Raman dados te?ricos e experimentais do cristal l-treonina. / In this work we present a study of the structural, electronic, optical and vibrational properties of orthorhombic l-threonine crystals, obtained through computational simulations in the DFT formalism (Density Functional Theory), in which local density approximations (LDA-CAPZ) and Of the generalized gradient (GGA-PBE). L-threonine is an essential amino acid that plays an important role in biological systems, being the last of the 20 amino acids that make up the proteins to be identi ed. For the crystal l-threonine, the optimization of crystalline geometry, lattice parameters, angles and inter atomic distances, band structure, state-by-atom density, optical absorption, dielectric function, refractive index, optical conductivity, loss function, infrared spectrum and Raman. The new lattice parameters found are close to the experimental values. A direct band gap E = 5.06 eV and an indirect band gap E (X! S) = 4.91 eV were obtained in the electronic structure for GGA and LDA approaches, respectively. The analysis of the electron states density allowed to identify the contributions per atom for the states in valence and conduction bands from the optical properties it is possible to observe a sensitivity to the plane of incident light polarization 001. A good agreement was obtained between the vibrational spectra IR and Raman theoretical and experimental data of the crystal l-threonine.