Density functional theory based calculations were performed to study the modification of the elec... more Density functional theory based calculations were performed to study the modification of the electronic and structural properties originating from the interaction between the (10,0) GaPNT and the FeCl3 and CrO3 compounds, using the software SIESTA. The results show that, for both compounds interacting with the GaPNT, the structures remained practically the same with a small deformation. In all studied systems, FeCl3 acts as an acceptor of electrons while CrO3 as an electron donor. The binding energy showed that both the FeCl3 and CrO3 compounds interact strongly with the GaPNT through a chemisorption process. Projected density of states analysis shows that the electronic properties were drastically modified with the adsorption of the FeCl3 compound on the GaPNT due to the appearance of localized states in the gap region. In all systems, the band gap was reduced except in the case of CrO3 adsorbed outside the GaPNT, in which the band gap was increased. In the case of FeCl3 adsorbed i...
The structural and electronic properties of FeCl and CrO interacting with (10,0) GaNNT were obtai... more The structural and electronic properties of FeCl and CrO interacting with (10,0) GaNNT were obtained using first principles calculations based on the density functional theory. The results show that for the CrO interacting with the GaNNT, the structure was locally deformed. However, in case of FeCl adsorbed with the GaNNT, the structure remained practically the same with the negligible deformation observed on tube surface. The projected density of states for the pristine GaNNT was modified with adsorption of FeCl molecule by the appearance of three strongly localized states in gap region. In case of GaNNT plus CrO molecule, one strongly localized level appeared in energy gap region with high contributions of molecule atoms. The analysis of the binding energy shows that the CrO interacting with the GaNNT is more favorable and the process occurs through chemisorption regime in both systems. Graphical Abstract Projected density of states of pristine GaNNT and FeCl interacting with GaNNT.
The structural and electronic properties of boron and nitrogen atom substitutional doping in (8,0... more The structural and electronic properties of boron and nitrogen atom substitutional doping in (8,0)@(13,0) (semiconductor@semiconductor) and (6,0)@(13,0) (metallic@semiconductor) double walled carbon nanotubes, were obtained by using the first-principle calculations based on the density functional theory. In this framework, the electronic density plays a central role and it was obtained from a self-consistent field form. When boron or nitrogen substitutes a carbon atom the structure remains practically the same with negligible deformation observed around defects in all configurations considered. The electronic band structure results indicate that the boron doped systems behave as a p-type impurity, however, the nitrogen doped systems behave as an n-type impurity. In all the systems investigated here, we found that, in the cases of semiconductor@semiconductor tubes, they were the easiest to incorporate a B atom in the outer-wall and an N atom in the inner-wall of the nanotube.
A detailed study involving non-metallic atoms (boron, nitrogen and carbon atoms) adsorbed on magn... more A detailed study involving non-metallic atoms (boron, nitrogen and carbon atoms) adsorbed on magnesium chloride (MgCl2) monolayers has been performed by density functional theory.
In this work, the interaction of GaN nanotube (GaNNT) with common air pollutants of industrialize... more In this work, the interaction of GaN nanotube (GaNNT) with common air pollutants of industrialized cities, such as NH3, NO2 and SO2 in different configurations was studied. For this study, the single-walled (10,0) GaNNT was used. The analysis was done via the density functional theory implemented in the SIESTA simulation software. The analysis of the results shows that the air pollutants alter the properties of nanotubes when they interact with them. The stability analysis shows that the most stable configurations are those in which adsorption occurs through a chemical process. The systems remain semiconductors, but in the case of NO2 and SO2 molecules interacting with GaNNT, there was a significant reduction in the energy gap. Our results also indicate that GaNNT is a promising material to detect and remove NH3 and NO2 molecules from the environment, however it may be not applicable to detect or remove SO2, because the latter interacts strongly with the nanotube, which prevents the...
High Pressure Raman scattering measurements of KDP:Mn were performed at room temperatures. The X-... more High Pressure Raman scattering measurements of KDP:Mn were performed at room temperatures. The X-ray powder diffraction patterns taken at room temperature by Rietveld refinement showed that doped samples of KDP-Mn have the same tetragonal structure of a pure KDP crystal, but with a contraction of the crystalline cell. The behavior of the Raman spectra, in particular the emergence of a new modes at 330 cm-1, indicates that KDP:Mn undergoes a structural phase transition with onset at around 4 GP. First principle density-functional theory (DFT) calculations indicate that tetrahedral rotation with pressure is predominantly around the c crystalline direction. Theoretical results indicates that pressure induced tetrahedral rotations leads to change tetrahedral neighborhood, activating librations/bending modes observed for high pressure phase of KDP:Mn with stronger Raman activity.
Este trabalho tem por objetivo refletir sobre aspectos da formação inicial de professores de Físi... more Este trabalho tem por objetivo refletir sobre aspectos da formação inicial de professores de Física a partir da perspectiva de estudantes do curso de Física Licenciatura da Universidade Federal do Maranhão. São apresentadas algumas problemáticas que interferem no processo de formação docente e contribuem para o elevado índice de evasão, assim como, se discute sobre o desenvolvimento da prática docente, nos primeiros anos do curso, analisando contribuições que algumas disciplinas e programas oferecem. Para embasar tais reflexões, além da análise do projeto pedagógico do curso, foi aplicado um questionário que coletou informações junto a estudantes, matriculados nas disciplinas Didática e Prática de Ensino I, ministradas no sexto e sétimo período, respectivamente. Os dados obtidos reafirmam prováveis motivos para a evasão do curso, entre eles, a falta de conhecimento de conceitos referentes a conteúdos da Educação Básica. Eles mostraram também, que estudantes que tiveram experiências ...
REAMEC - Rede Amazônica de Educação em Ciências e Matemática
Neste trabalho, procuraremos fazer um relato da história do ensino de física no Brasil no período... more Neste trabalho, procuraremos fazer um relato da história do ensino de física no Brasil no período de 1549-1930. Objetivamos com isso encontrar evidências do processo de disseminação do conhecimento científico no país. A pesquisa foi realizada através de consultas a artigos científicos e teses que tratavam do ensino no Brasil colonial, imperial e republicano. A pesquisa revela a pouca importância da física e das ciências naturais, uma vez que, no período investigado, as disciplinas de caráter humanística eram consideradas relevantes para a formação do cidadão e definidas como disciplinas preparatórias para o ingresso no ensino superior. Por outro lado, também verificamos que fatores políticos, sociais e econômicos, influenciaram o ensino de física. Analisar a história do ensino de física, através do recorte temporal escolhido, permitiu-nos compreender os conhecimentos científicos ligados às relações estabelecidas entre a ciência e sociedade em diferentes épocas.
Este trabalho é resultado de uma pesquisa de caráter experimental realizada em uma escola pública... more Este trabalho é resultado de uma pesquisa de caráter experimental realizada em uma escola pública estadual na cidade de São Luís, Maranhão, durante o primeiro semestre de 2015. A pesquisa foi desenvolvida pensando nas dificuldades relatadas pelos professores e alunos relativos ao ensino e a aprendizagem dos temas eletrostática e eletromagnetismo na abordagem sobre força elétrica, campo elétrico, resistores e suas associações, magnetismo, indução magnética, geradores e capacitores e suas associações, dentre outros assuntos. As simulações computacionais e os experimentos foram utilizados como ferramentas auxiliares no processo de aprendizagem de alunos do terceiro ano do ensino médio, seguindo três etapas: inicialmente, aplicou-se um questionário para verificar conhecimentos específicos dos temas a serem abordados; na segunda etapa, foram realizadas atividades utilizando simulações computacionais e práticas experimentais; e, por último, foi reaplicado o questionário inicial, a fim de...
Este trabalho apresenta um recorte bibliografico das producoes academicas brasileiras que investi... more Este trabalho apresenta um recorte bibliografico das producoes academicas brasileiras que investigaram a forma que os livros didaticos de Fisica do Ensino Medio apresentam os conteudos de Fisica Moderna e Contemporânea (FMC). A pesquisa busca investigar como tem sido desenvolvidos os trabalhos nessa area de pesquisa e quais encaminhamentos os autores de livros didaticos atribuem a FMC. O estudo foi desenvolvido com base em pesquisas registradas no Banco de Teses e Dissertacoes da Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (Capes), referente ao periodo de 2008 a 2017. Os trabalhos analisados mostram que a abordagem da FMC nos livros didaticos nao seguem as recomendacoes dos documentos oficiais de Educacao.
This paper deals with quantum mechanical interaction of no 3− with (5,5) and (8,0) swcnts. To per... more This paper deals with quantum mechanical interaction of no 3− with (5,5) and (8,0) swcnts. To perform this we have made an ab initio calculation based on the density functional theory. In these framework the electronic density plays a central role and it was obtained of a self-consistent field form. It was observed through binding energy that NO3− molecule interacts with each nanotube in a physisorption regime. We propose these swcnts as a potential filter device due to reasonable interaction with NO3− molecule. Besides this type of filter could be reusable, therefore after the filtering, the swcnts could be separated from NO3− molecule.
Density functional theory based calculations were performed to study the modification of the elec... more Density functional theory based calculations were performed to study the modification of the electronic and structural properties originating from the interaction between the (10,0) GaPNT and the FeCl3 and CrO3 compounds, using the software SIESTA. The results show that, for both compounds interacting with the GaPNT, the structures remained practically the same with a small deformation. In all studied systems, FeCl3 acts as an acceptor of electrons while CrO3 as an electron donor. The binding energy showed that both the FeCl3 and CrO3 compounds interact strongly with the GaPNT through a chemisorption process. Projected density of states analysis shows that the electronic properties were drastically modified with the adsorption of the FeCl3 compound on the GaPNT due to the appearance of localized states in the gap region. In all systems, the band gap was reduced except in the case of CrO3 adsorbed outside the GaPNT, in which the band gap was increased. In the case of FeCl3 adsorbed i...
The structural and electronic properties of FeCl and CrO interacting with (10,0) GaNNT were obtai... more The structural and electronic properties of FeCl and CrO interacting with (10,0) GaNNT were obtained using first principles calculations based on the density functional theory. The results show that for the CrO interacting with the GaNNT, the structure was locally deformed. However, in case of FeCl adsorbed with the GaNNT, the structure remained practically the same with the negligible deformation observed on tube surface. The projected density of states for the pristine GaNNT was modified with adsorption of FeCl molecule by the appearance of three strongly localized states in gap region. In case of GaNNT plus CrO molecule, one strongly localized level appeared in energy gap region with high contributions of molecule atoms. The analysis of the binding energy shows that the CrO interacting with the GaNNT is more favorable and the process occurs through chemisorption regime in both systems. Graphical Abstract Projected density of states of pristine GaNNT and FeCl interacting with GaNNT.
The structural and electronic properties of boron and nitrogen atom substitutional doping in (8,0... more The structural and electronic properties of boron and nitrogen atom substitutional doping in (8,0)@(13,0) (semiconductor@semiconductor) and (6,0)@(13,0) (metallic@semiconductor) double walled carbon nanotubes, were obtained by using the first-principle calculations based on the density functional theory. In this framework, the electronic density plays a central role and it was obtained from a self-consistent field form. When boron or nitrogen substitutes a carbon atom the structure remains practically the same with negligible deformation observed around defects in all configurations considered. The electronic band structure results indicate that the boron doped systems behave as a p-type impurity, however, the nitrogen doped systems behave as an n-type impurity. In all the systems investigated here, we found that, in the cases of semiconductor@semiconductor tubes, they were the easiest to incorporate a B atom in the outer-wall and an N atom in the inner-wall of the nanotube.
A detailed study involving non-metallic atoms (boron, nitrogen and carbon atoms) adsorbed on magn... more A detailed study involving non-metallic atoms (boron, nitrogen and carbon atoms) adsorbed on magnesium chloride (MgCl2) monolayers has been performed by density functional theory.
In this work, the interaction of GaN nanotube (GaNNT) with common air pollutants of industrialize... more In this work, the interaction of GaN nanotube (GaNNT) with common air pollutants of industrialized cities, such as NH3, NO2 and SO2 in different configurations was studied. For this study, the single-walled (10,0) GaNNT was used. The analysis was done via the density functional theory implemented in the SIESTA simulation software. The analysis of the results shows that the air pollutants alter the properties of nanotubes when they interact with them. The stability analysis shows that the most stable configurations are those in which adsorption occurs through a chemical process. The systems remain semiconductors, but in the case of NO2 and SO2 molecules interacting with GaNNT, there was a significant reduction in the energy gap. Our results also indicate that GaNNT is a promising material to detect and remove NH3 and NO2 molecules from the environment, however it may be not applicable to detect or remove SO2, because the latter interacts strongly with the nanotube, which prevents the...
High Pressure Raman scattering measurements of KDP:Mn were performed at room temperatures. The X-... more High Pressure Raman scattering measurements of KDP:Mn were performed at room temperatures. The X-ray powder diffraction patterns taken at room temperature by Rietveld refinement showed that doped samples of KDP-Mn have the same tetragonal structure of a pure KDP crystal, but with a contraction of the crystalline cell. The behavior of the Raman spectra, in particular the emergence of a new modes at 330 cm-1, indicates that KDP:Mn undergoes a structural phase transition with onset at around 4 GP. First principle density-functional theory (DFT) calculations indicate that tetrahedral rotation with pressure is predominantly around the c crystalline direction. Theoretical results indicates that pressure induced tetrahedral rotations leads to change tetrahedral neighborhood, activating librations/bending modes observed for high pressure phase of KDP:Mn with stronger Raman activity.
Este trabalho tem por objetivo refletir sobre aspectos da formação inicial de professores de Físi... more Este trabalho tem por objetivo refletir sobre aspectos da formação inicial de professores de Física a partir da perspectiva de estudantes do curso de Física Licenciatura da Universidade Federal do Maranhão. São apresentadas algumas problemáticas que interferem no processo de formação docente e contribuem para o elevado índice de evasão, assim como, se discute sobre o desenvolvimento da prática docente, nos primeiros anos do curso, analisando contribuições que algumas disciplinas e programas oferecem. Para embasar tais reflexões, além da análise do projeto pedagógico do curso, foi aplicado um questionário que coletou informações junto a estudantes, matriculados nas disciplinas Didática e Prática de Ensino I, ministradas no sexto e sétimo período, respectivamente. Os dados obtidos reafirmam prováveis motivos para a evasão do curso, entre eles, a falta de conhecimento de conceitos referentes a conteúdos da Educação Básica. Eles mostraram também, que estudantes que tiveram experiências ...
REAMEC - Rede Amazônica de Educação em Ciências e Matemática
Neste trabalho, procuraremos fazer um relato da história do ensino de física no Brasil no período... more Neste trabalho, procuraremos fazer um relato da história do ensino de física no Brasil no período de 1549-1930. Objetivamos com isso encontrar evidências do processo de disseminação do conhecimento científico no país. A pesquisa foi realizada através de consultas a artigos científicos e teses que tratavam do ensino no Brasil colonial, imperial e republicano. A pesquisa revela a pouca importância da física e das ciências naturais, uma vez que, no período investigado, as disciplinas de caráter humanística eram consideradas relevantes para a formação do cidadão e definidas como disciplinas preparatórias para o ingresso no ensino superior. Por outro lado, também verificamos que fatores políticos, sociais e econômicos, influenciaram o ensino de física. Analisar a história do ensino de física, através do recorte temporal escolhido, permitiu-nos compreender os conhecimentos científicos ligados às relações estabelecidas entre a ciência e sociedade em diferentes épocas.
Este trabalho é resultado de uma pesquisa de caráter experimental realizada em uma escola pública... more Este trabalho é resultado de uma pesquisa de caráter experimental realizada em uma escola pública estadual na cidade de São Luís, Maranhão, durante o primeiro semestre de 2015. A pesquisa foi desenvolvida pensando nas dificuldades relatadas pelos professores e alunos relativos ao ensino e a aprendizagem dos temas eletrostática e eletromagnetismo na abordagem sobre força elétrica, campo elétrico, resistores e suas associações, magnetismo, indução magnética, geradores e capacitores e suas associações, dentre outros assuntos. As simulações computacionais e os experimentos foram utilizados como ferramentas auxiliares no processo de aprendizagem de alunos do terceiro ano do ensino médio, seguindo três etapas: inicialmente, aplicou-se um questionário para verificar conhecimentos específicos dos temas a serem abordados; na segunda etapa, foram realizadas atividades utilizando simulações computacionais e práticas experimentais; e, por último, foi reaplicado o questionário inicial, a fim de...
Este trabalho apresenta um recorte bibliografico das producoes academicas brasileiras que investi... more Este trabalho apresenta um recorte bibliografico das producoes academicas brasileiras que investigaram a forma que os livros didaticos de Fisica do Ensino Medio apresentam os conteudos de Fisica Moderna e Contemporânea (FMC). A pesquisa busca investigar como tem sido desenvolvidos os trabalhos nessa area de pesquisa e quais encaminhamentos os autores de livros didaticos atribuem a FMC. O estudo foi desenvolvido com base em pesquisas registradas no Banco de Teses e Dissertacoes da Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (Capes), referente ao periodo de 2008 a 2017. Os trabalhos analisados mostram que a abordagem da FMC nos livros didaticos nao seguem as recomendacoes dos documentos oficiais de Educacao.
This paper deals with quantum mechanical interaction of no 3− with (5,5) and (8,0) swcnts. To per... more This paper deals with quantum mechanical interaction of no 3− with (5,5) and (8,0) swcnts. To perform this we have made an ab initio calculation based on the density functional theory. In these framework the electronic density plays a central role and it was obtained of a self-consistent field form. It was observed through binding energy that NO3− molecule interacts with each nanotube in a physisorption regime. We propose these swcnts as a potential filter device due to reasonable interaction with NO3− molecule. Besides this type of filter could be reusable, therefore after the filtering, the swcnts could be separated from NO3− molecule.
Uploads
Papers by S. Guerini