R. Mota - Academia.edu (original) (raw)
Papers by R. Mota
Physical Review B, 2001
Electronic and structural properties of silicon-doped carbon nanotubes. RJ Baierle Centro Univers... more Electronic and structural properties of silicon-doped carbon nanotubes. RJ Baierle Centro Universitário Franciscano, Departamento de Ciências Exatas, Santa Maria, 97010-032, RS, Brazil. Solange B. Fagan and R. Mota Departamento ...
Health Technol Assess, 2004
Reports are published in the HTA monograph series if (1) they have resulted from work commissione... more Reports are published in the HTA monograph series if (1) they have resulted from work commissioned for the HTA Programme, and (2) they are of a sufficiently high scientific quality as assessed by the referees and editors.
Physical Review B, 2000
Self-interstitial defect in germanium. Antônio JR da Silva, A. Janotti, and A. Fazzio Instituto d... more Self-interstitial defect in germanium. Antônio JR da Silva, A. Janotti, and A. Fazzio Instituto de Física, Universidade de São Paulo, Caixa Postal 66318, 05315-970, São Paulo, SP, Brazil. RJ Baierle Departamento de Ciências ...
Physical Review B, 2003
Ab initio study of an iron atom interacting with single-wall carbon nanotubes. Solange B. Fagan a... more Ab initio study of an iron atom interacting with single-wall carbon nanotubes. Solange B. Fagan and R. Mota Departamento de Física, Universidade Federal de Santa Maria, CEP 97105-900 Santa Maria, RS, Brazil. Antônio JR ...
IEEE International Conference on Electric Machines and Drives, 2005., 2005
Time domain terminal models for high voltage induction motor windings are developed for simulatin... more Time domain terminal models for high voltage induction motor windings are developed for simulating transient overvoltages due to switching operations in industrial installations. The models are based on the network synthesis of the terminal impedance for short circuit and open circuit conditions of the winding. The process of synthesis is carried out taking into account the minimum and maximum resonant frequencies. The machine winding impedance is determined with a frequency domain model developed by means of the transmission line theory and using a finite element method for electrical parameter calculation. The computer models are validated by comparing the calculated transient overvoltages and the winding impedances against test data for a high voltage motor
The Journal of Physical Chemistry C, 2008
Physical Review C, 1999
We used the N⌬ and ⌬⌬ potentials derived from the chiral quark cluster model to analyze the bound... more We used the N⌬ and ⌬⌬ potentials derived from the chiral quark cluster model to analyze the bound-state problem of the N⌬ and N⌬⌬ systems when the two-body subsystems can be in S-wave states. We found that the N⌬ system has only one bound state right at the N⌬ threshold while for the N⌬⌬ system there are no bound-state solutions in any of the allowed channels, although a couple of them are nearly bound. Our model predicts the NN 1 D 2 resonance as being a bound state of the N⌬ system at the N⌬ threshold.
Physical Review B, 2000
Microscopic picture of the single vacancy in germanium. A. Fazzio, A. Janotti, and Antônio JR da ... more Microscopic picture of the single vacancy in germanium. A. Fazzio, A. Janotti, and Antônio JR da Silva Instituto de Física, Universidade de São Paulo, CP 66318, 05315-970 São Paulo, SP, Brazil. R. Mota Departamento de Física ...
Physical Review B, 2009
... Lett. 98, 196803 [?]2007[?]. 13 TB Martins, RH Miwa, AJR da Silva, and A. Fazzio, 1 K. Nano L... more ... Lett. 98, 196803 [?]2007[?]. 13 TB Martins, RH Miwa, AJR da Silva, and A. Fazzio, 1 K. Nano Lett. 8, 2293 [?]2008[?]. Banhart, JC Charlier, and PM Ajayan, Phys. ... 16 Y. Yagi, TM Briere, MHF Sluiter, V. Kumar, AA Farajian, and Y. Kawazoe, Phys. Rev. B 69, 075414 [?]2004[?]. ...
Physica B: Condensed Matter, 2001
ABSTRACT We study, using first principles calculations, the electronic and structural properties ... more ABSTRACT We study, using first principles calculations, the electronic and structural properties of an isolated vacancy and self-interstitial defects in germanium. For the vacancy we analyze the lattice relaxations for the charge states (++), (+), and (0), and show that the atomic displacements, albeit small, are not completely negligible for the second-nearest-neighbor atoms to the vacancy site. Moreover, we show that the relaxations decay slowly along the zigzags that go through the vacancy site. For the self-interstitial we present an analysis of the charge density, which supports the description of this defect as a four-atoms ring strongly attached to the lattice, which we have named a kite-defect.
Physica B: Condensed Matter, 1999
... A Janotti a , R Baierle b , Antônio JR da Silva a , R Mota b and A Fazzio a , Corresponding A... more ... A Janotti a , R Baierle b , Antônio JR da Silva a , R Mota b and A Fazzio a , Corresponding Author Contact Information , E-mail The Corresponding Author. a Instituto de Fı́sica, Universidade de São Paulo, CP 66318, 05315-970 São Paulo, SP, Brazil. ...
Physica B: Condensed Matter, 2003
We study the structural, electronic and magnetic properties of Fe and Mn monomers and dimers adso... more We study the structural, electronic and magnetic properties of Fe and Mn monomers and dimers adsorbed on a semiconductor (8,0) single-wall carbon nanotube. Using spin-polarized total-energy ab initio calculations based on the density-functional theory, we find for both Fe and Mn monomers the hexagonal center as the most stable adsorption site. For Fe dimers in the most stable configuration, the atoms are on opposite C-C bond-centered positions (BC-BC), with an Fe-Fe distance of 2.23 ( A. For Mn dimers, on the other hand, the most stable configurations are found to be with the Mn atoms adsorbed on top of C atoms, for a high-spin state (Mn-Mn distance of 2.6 ( A), and a slightly lowerenergy BC-BC configuration for the low-spin state (Mn-Mn distance of 2.53 ( A). These results show that the dimer configurations are not simply related to the isolated monomer structures. The resulting magnetic moments for the adsorbed dimers are found to be similar to their corresponding values in the free diatomic molecules. r
Nanotechnology, 2006
The electronic and structural properties of an (8, 0) single-walled carbon nanotube (SWNT) with a... more The electronic and structural properties of an (8, 0) single-walled carbon nanotube (SWNT) with a single vacancy and interacting with a Si atom are studied using first principles calculations based on the density-functional theory. Initially, the Si atom is positioned in the site above the vacancy, with its position fixed until the nanotube geometry is fully relaxed. After that, the Si atom approaches the tube and it is shown that one C atom is displaced outwards forming a bump. The final configuration, as well as each step of the process, is studied in detail and the resulting band structures and the total charge densities are systematically analysed.
Nano Letters, 2005
The electronic and structural properties of a single-walled carbon nanotube (SWNT) under mechanic... more The electronic and structural properties of a single-walled carbon nanotube (SWNT) under mechanical deformation are studied using first-principles calculations based on the density functional theory. A force is applied over one particular C-atom with enough strength to break the chemical bonds between the atom and its nearest neighbors, leading to a final configuration represented by one tube with a vacancy and an isolated C-atom inside the tube. Our investigation demonstrates that there is a tendency that the first bond to break is the one most parallel possible to the tube axis and, after, the remaining two other bonds are broken. The analysis of the electronic charge densities, just before and after the bonds breaking, helps to elucidate how the vacancy is formed on an atom-by-atom basis. In particular, for tubes with a diameter around 11 angstroms, it is shown that the chemical bonds start to break only when the externally applied force is of the order of 14 nN and it is independent of the chirality. The formation energies for the vacancies created using this process are almost independent of the chirality, otherwise the bonds broken and the reconstruction are dependent.
Microelectronics Journal, 2003
In this work the structural, electronic and magnetic properties of one-dimensional Fe chains inte... more In this work the structural, electronic and magnetic properties of one-dimensional Fe chains interacting with a semiconductor single-wall carbon nanotube are investigated using first-principles spin-polarized calculations. A systematic study of several configurations of a Fe wire interacting with a nanotube both from outside as well as inside is presented, and the resulting equilibrium distances, binding energies and magnetizations are discussed. The most stable configurations are compared with previous results obtained for a single Fe atom interacting with the tube.
Microelectronics Journal, 2009
Electronic and structural properties of carbon nanotubes interacting with vitamins C and B3 radic... more Electronic and structural properties of carbon nanotubes interacting with vitamins C and B3 radicals are analyzed through the density functional theory. The radical adsorptions result in modifications on the structural and electronic properties of the original carbon nanotubes. The strong adsorptions resulting from the combination of the carbon nanotubes with ascorbic acid and nicotinamide allow the manipulation of the resulting systems in a stable way. These results are extremely relevant in order to identify the potential applications of functionalized carbon nanotubes as drug delivery systems or molecule sensors.
Journal of the Brazilian Chemical Society, 2010
... with diode array detector and liquid chromatography-tandem mass spectrometry Caldas, Sergiane... more ... with diode array detector and liquid chromatography-tandem mass spectrometry Caldas, Sergiane S.; Demoliner, Adriana; Costa, Fabiane P.; D ... activities Paula, Fávero R.; Trossini, Gustavo HG; Ferreira, Elizabeth I.; Serrano, Silvia HP; Menezes, Carla MS; Tavares, Leoberto C. ...
Journal of Physics: Condensed Matter, 2004
... J. Phys.: Condens. Matter 16 (2004) 36473661 PII: S0953-8984(04)76961-1 An ab initio study o... more ... J. Phys.: Condens. Matter 16 (2004) 36473661 PII: S0953-8984(04)76961-1 An ab initio study of manganese atoms and wires interacting with carbon nanotubes Solange B Fagan1, R Mota2, Antônio JR da Silva3 and A Fazzio3 ...
International Journal of Quantum Chemistry, 1995
This contribution is concerned with the occurrence of metallic character in K-doped systems and t... more This contribution is concerned with the occurrence of metallic character in K-doped systems and the non-occurrence in Na-doped systems. An N-fold degenerate Hubbard model in the Gutzwiller approximation is utilized to discuss the meal-insulator transitions observed in these alkali-doped fullerides. The parameters used are derived from INDO calculations in the molecular cluster approach. 9 refs., 2 figs.
Physical Review B, 2001
Electronic and structural properties of silicon-doped carbon nanotubes. RJ Baierle Centro Univers... more Electronic and structural properties of silicon-doped carbon nanotubes. RJ Baierle Centro Universitário Franciscano, Departamento de Ciências Exatas, Santa Maria, 97010-032, RS, Brazil. Solange B. Fagan and R. Mota Departamento ...
Health Technol Assess, 2004
Reports are published in the HTA monograph series if (1) they have resulted from work commissione... more Reports are published in the HTA monograph series if (1) they have resulted from work commissioned for the HTA Programme, and (2) they are of a sufficiently high scientific quality as assessed by the referees and editors.
Physical Review B, 2000
Self-interstitial defect in germanium. Antônio JR da Silva, A. Janotti, and A. Fazzio Instituto d... more Self-interstitial defect in germanium. Antônio JR da Silva, A. Janotti, and A. Fazzio Instituto de Física, Universidade de São Paulo, Caixa Postal 66318, 05315-970, São Paulo, SP, Brazil. RJ Baierle Departamento de Ciências ...
Physical Review B, 2003
Ab initio study of an iron atom interacting with single-wall carbon nanotubes. Solange B. Fagan a... more Ab initio study of an iron atom interacting with single-wall carbon nanotubes. Solange B. Fagan and R. Mota Departamento de Física, Universidade Federal de Santa Maria, CEP 97105-900 Santa Maria, RS, Brazil. Antônio JR ...
IEEE International Conference on Electric Machines and Drives, 2005., 2005
Time domain terminal models for high voltage induction motor windings are developed for simulatin... more Time domain terminal models for high voltage induction motor windings are developed for simulating transient overvoltages due to switching operations in industrial installations. The models are based on the network synthesis of the terminal impedance for short circuit and open circuit conditions of the winding. The process of synthesis is carried out taking into account the minimum and maximum resonant frequencies. The machine winding impedance is determined with a frequency domain model developed by means of the transmission line theory and using a finite element method for electrical parameter calculation. The computer models are validated by comparing the calculated transient overvoltages and the winding impedances against test data for a high voltage motor
The Journal of Physical Chemistry C, 2008
Physical Review C, 1999
We used the N⌬ and ⌬⌬ potentials derived from the chiral quark cluster model to analyze the bound... more We used the N⌬ and ⌬⌬ potentials derived from the chiral quark cluster model to analyze the bound-state problem of the N⌬ and N⌬⌬ systems when the two-body subsystems can be in S-wave states. We found that the N⌬ system has only one bound state right at the N⌬ threshold while for the N⌬⌬ system there are no bound-state solutions in any of the allowed channels, although a couple of them are nearly bound. Our model predicts the NN 1 D 2 resonance as being a bound state of the N⌬ system at the N⌬ threshold.
Physical Review B, 2000
Microscopic picture of the single vacancy in germanium. A. Fazzio, A. Janotti, and Antônio JR da ... more Microscopic picture of the single vacancy in germanium. A. Fazzio, A. Janotti, and Antônio JR da Silva Instituto de Física, Universidade de São Paulo, CP 66318, 05315-970 São Paulo, SP, Brazil. R. Mota Departamento de Física ...
Physical Review B, 2009
... Lett. 98, 196803 [?]2007[?]. 13 TB Martins, RH Miwa, AJR da Silva, and A. Fazzio, 1 K. Nano L... more ... Lett. 98, 196803 [?]2007[?]. 13 TB Martins, RH Miwa, AJR da Silva, and A. Fazzio, 1 K. Nano Lett. 8, 2293 [?]2008[?]. Banhart, JC Charlier, and PM Ajayan, Phys. ... 16 Y. Yagi, TM Briere, MHF Sluiter, V. Kumar, AA Farajian, and Y. Kawazoe, Phys. Rev. B 69, 075414 [?]2004[?]. ...
Physica B: Condensed Matter, 2001
ABSTRACT We study, using first principles calculations, the electronic and structural properties ... more ABSTRACT We study, using first principles calculations, the electronic and structural properties of an isolated vacancy and self-interstitial defects in germanium. For the vacancy we analyze the lattice relaxations for the charge states (++), (+), and (0), and show that the atomic displacements, albeit small, are not completely negligible for the second-nearest-neighbor atoms to the vacancy site. Moreover, we show that the relaxations decay slowly along the zigzags that go through the vacancy site. For the self-interstitial we present an analysis of the charge density, which supports the description of this defect as a four-atoms ring strongly attached to the lattice, which we have named a kite-defect.
Physica B: Condensed Matter, 1999
... A Janotti a , R Baierle b , Antônio JR da Silva a , R Mota b and A Fazzio a , Corresponding A... more ... A Janotti a , R Baierle b , Antônio JR da Silva a , R Mota b and A Fazzio a , Corresponding Author Contact Information , E-mail The Corresponding Author. a Instituto de Fı́sica, Universidade de São Paulo, CP 66318, 05315-970 São Paulo, SP, Brazil. ...
Physica B: Condensed Matter, 2003
We study the structural, electronic and magnetic properties of Fe and Mn monomers and dimers adso... more We study the structural, electronic and magnetic properties of Fe and Mn monomers and dimers adsorbed on a semiconductor (8,0) single-wall carbon nanotube. Using spin-polarized total-energy ab initio calculations based on the density-functional theory, we find for both Fe and Mn monomers the hexagonal center as the most stable adsorption site. For Fe dimers in the most stable configuration, the atoms are on opposite C-C bond-centered positions (BC-BC), with an Fe-Fe distance of 2.23 ( A. For Mn dimers, on the other hand, the most stable configurations are found to be with the Mn atoms adsorbed on top of C atoms, for a high-spin state (Mn-Mn distance of 2.6 ( A), and a slightly lowerenergy BC-BC configuration for the low-spin state (Mn-Mn distance of 2.53 ( A). These results show that the dimer configurations are not simply related to the isolated monomer structures. The resulting magnetic moments for the adsorbed dimers are found to be similar to their corresponding values in the free diatomic molecules. r
Nanotechnology, 2006
The electronic and structural properties of an (8, 0) single-walled carbon nanotube (SWNT) with a... more The electronic and structural properties of an (8, 0) single-walled carbon nanotube (SWNT) with a single vacancy and interacting with a Si atom are studied using first principles calculations based on the density-functional theory. Initially, the Si atom is positioned in the site above the vacancy, with its position fixed until the nanotube geometry is fully relaxed. After that, the Si atom approaches the tube and it is shown that one C atom is displaced outwards forming a bump. The final configuration, as well as each step of the process, is studied in detail and the resulting band structures and the total charge densities are systematically analysed.
Nano Letters, 2005
The electronic and structural properties of a single-walled carbon nanotube (SWNT) under mechanic... more The electronic and structural properties of a single-walled carbon nanotube (SWNT) under mechanical deformation are studied using first-principles calculations based on the density functional theory. A force is applied over one particular C-atom with enough strength to break the chemical bonds between the atom and its nearest neighbors, leading to a final configuration represented by one tube with a vacancy and an isolated C-atom inside the tube. Our investigation demonstrates that there is a tendency that the first bond to break is the one most parallel possible to the tube axis and, after, the remaining two other bonds are broken. The analysis of the electronic charge densities, just before and after the bonds breaking, helps to elucidate how the vacancy is formed on an atom-by-atom basis. In particular, for tubes with a diameter around 11 angstroms, it is shown that the chemical bonds start to break only when the externally applied force is of the order of 14 nN and it is independent of the chirality. The formation energies for the vacancies created using this process are almost independent of the chirality, otherwise the bonds broken and the reconstruction are dependent.
Microelectronics Journal, 2003
In this work the structural, electronic and magnetic properties of one-dimensional Fe chains inte... more In this work the structural, electronic and magnetic properties of one-dimensional Fe chains interacting with a semiconductor single-wall carbon nanotube are investigated using first-principles spin-polarized calculations. A systematic study of several configurations of a Fe wire interacting with a nanotube both from outside as well as inside is presented, and the resulting equilibrium distances, binding energies and magnetizations are discussed. The most stable configurations are compared with previous results obtained for a single Fe atom interacting with the tube.
Microelectronics Journal, 2009
Electronic and structural properties of carbon nanotubes interacting with vitamins C and B3 radic... more Electronic and structural properties of carbon nanotubes interacting with vitamins C and B3 radicals are analyzed through the density functional theory. The radical adsorptions result in modifications on the structural and electronic properties of the original carbon nanotubes. The strong adsorptions resulting from the combination of the carbon nanotubes with ascorbic acid and nicotinamide allow the manipulation of the resulting systems in a stable way. These results are extremely relevant in order to identify the potential applications of functionalized carbon nanotubes as drug delivery systems or molecule sensors.
Journal of the Brazilian Chemical Society, 2010
... with diode array detector and liquid chromatography-tandem mass spectrometry Caldas, Sergiane... more ... with diode array detector and liquid chromatography-tandem mass spectrometry Caldas, Sergiane S.; Demoliner, Adriana; Costa, Fabiane P.; D ... activities Paula, Fávero R.; Trossini, Gustavo HG; Ferreira, Elizabeth I.; Serrano, Silvia HP; Menezes, Carla MS; Tavares, Leoberto C. ...
Journal of Physics: Condensed Matter, 2004
... J. Phys.: Condens. Matter 16 (2004) 36473661 PII: S0953-8984(04)76961-1 An ab initio study o... more ... J. Phys.: Condens. Matter 16 (2004) 36473661 PII: S0953-8984(04)76961-1 An ab initio study of manganese atoms and wires interacting with carbon nanotubes Solange B Fagan1, R Mota2, Antônio JR da Silva3 and A Fazzio3 ...
International Journal of Quantum Chemistry, 1995
This contribution is concerned with the occurrence of metallic character in K-doped systems and t... more This contribution is concerned with the occurrence of metallic character in K-doped systems and the non-occurrence in Na-doped systems. An N-fold degenerate Hubbard model in the Gutzwiller approximation is utilized to discuss the meal-insulator transitions observed in these alkali-doped fullerides. The parameters used are derived from INDO calculations in the molecular cluster approach. 9 refs., 2 figs.