CRISTIANO BASTOS - Academia.edu (original) (raw)

Papers by CRISTIANO BASTOS

Journal of Photochemistry and Photobiology A: Chemistry, 2006

... The sparkle parameters that were optimized, are all related to the core–core repulsion energy... more ... The sparkle parameters that were optimized, are all related to the core–core repulsion energy between atoms A and B, E N (A, B), which, in the semiempirical method AM1, is [18]:(1) where 〈S A S A |S B S B 〉 is parameter GSS; α A or α B are ALP, a parameter representing the ...

Química Nova, 2023

Ignis fatuus, a luminous phenomenon witnessed over the centuries by observers around the world, i... more Ignis fatuus, a luminous phenomenon witnessed over the centuries by observers around the world, is no longer seen in modern times, suggesting that it is extinct. An explanation for this disappearance can be found in the description of ignis fatuus as a cool flame of methane. Unlike a conventional flame, which generates large amounts of heat, ignis fatuus is a flame that glows without heat through a chemiluminescence process. Its characteristic bluish color is due to the emission of excited formaldehyde, which is formed in the slow combustion of methane. It is generally accepted that the phenomenon is a spontaneous combustion of swamp gas in contact with the oxygen in air, but an analysis of the energies involved in the cool flame process indicates that the phenomenon is not spontaneous in nature. Experiments carried out in the 19th century show torches being used to ignite ignis fatuus. The abandonment of fire in favor of night lighting may hold the secret to this mystery of ignis fatuus's extinction.

Orbital: The Electronic Journal of Chemistry, 2017

In this paper, we analyze and validate of an alternative proposal for the understanding and inter... more In this paper, we analyze and validate of an alternative proposal for the understanding and interpretation of the dipole moment of diatomic molecules, content present in the curriculum of disciplines physical chemistry and quantum chemistry in undergraduate chemistry courses. For this, 87 students participating the degree course in chemistry at a university in Brazil, they used computational chemistry calculations and analytical calculations for the dipole moment of the considered molecules. Results show the proposed method can be an alternative for calculations involving dipole moment of diatomic molecules.

Chinese Physics C, 2021

A rovibrational model, including anharmonic, centrifugal, and Coriolis corrections, is used to ca... more A rovibrational model, including anharmonic, centrifugal, and Coriolis corrections, is used to calculate π, K,N, and Ʃ orbital and radial resonances. The four orbital excitations of the π meson correspond to the b(1235), π2(1670), b 3(2030), and π4(2250) resonances. Its first four radial excitations correspond to the π(1300), π(1800), π(2070), and π(2360) resonances. The orbital excitations of the K meson are interpreted as the K 1(1270), K 2(1770), K 3(2320), and K 4(2500) resonances; its radial excitations correspond to the K(1460) and K(1830) resonances. The N orbital excitations are identified with the N(1520), N(1680), N(2190), N(2220), and N(2600) resonances. The first four radial excitations of the N family correspond to the N(1440), N(1880), N(2100), and N(2300) resonances. The orbital excitations of the Ʃ baryon are associated with the Ʃ(1670), Ʃ(1915), Ʃ(2100), and Ʃ(2250) resonances, whereas its radial excitations are identified with the Ʃ(1660), Ʃ(1770), and Ʃ(1880) reso...

Theoretical Chemistry Accounts, 2020

Using a BCS-adapted equation via multivariate analysis of structural and electronic properties, w... more Using a BCS-adapted equation via multivariate analysis of structural and electronic properties, we calculated the critical temperature of fullerides A 2 BC 60 and A 3 C 60 , with pure A and B alkaline metal or solvated with NH 3 and CH 3 NH 2 , in good agreement with the experimental data. In the ammoniation of Na 2 CsC 60 , concomitant expansion of the lattice and the increasing ionic character of the chemical bonds between the ligands and C 60 , the critical temperature rises by about 20 K. For methylamine, there is an increase in critical temperature far lower than with ammonia, indicating that anisotropic lattice expansion does not favor the phenomenon. Besides crystal lattice expansion, a known factor that influences the critical temperature, our model identifies the other structural and electronic factors that contribute to the critical temperature of these materials. In alkali metal hydration, the crystal is expanded at the same time that the HOMO-LUMO gap is reduced, favoring electron transfer between the metal-ligand complex and C 60. With the intercalation of water molecules in these fullerides, we predict that Na 3 C 60 becomes superconducting at a critical temperature of 47.2 K and that Cs 3 C 60 reaches 50 K.

Journal of Mathematical Chemistry, 2016

The intrinsic geometric approach to quantum mechanics has been applied to study nanostructures, a... more The intrinsic geometric approach to quantum mechanics has been applied to study nanostructures, as well as aromaticity and other electronic properties of molecules. Usually strong hypotheses on the geometry are made in order to allow for analytical solutions. We undertake the problem of stability, with respect to smooth deformations, of the spectra obtained under such simplifying hypotheses. In this article we show that symmetries can sometimes be removed by solving the problem of a particle constrained to a right cylinder with an arbitrary smooth cross section considering the effects of intrinsic geometry. The topology of the cross section, rather than its geometry, is shown to play a key role in this context. Our solution is applied to a generalized Möbius strip when the median curve is nearly a circle of diameter sufficiently large compared to the width of the strip. We also provide a systematic method for ordering the quantum states of generalized right cylinders according to their energies and apply this method to order the spectra of Möbius strips whose diameters are much larger than their widths. Finally, for the sake of comparison, our results are used to calculate the \uppi π electron energy spectra of five aromatic molecules (benzene, pyrazine, pyridine, 1,3 diazyne and 1,3,5 triazyne), showing a fair agreement with experimental data and quantum chemistry calculations.

Journal of Superconductivity and Novel Magnetism, 2016

The charge distribution and electronic properties of several materials that become superconductor... more The charge distribution and electronic properties of several materials that become superconductors at a low temperature are examined by using Density Functional Theory cluster calculations. For cuprates, charge transfer occurs between copper atoms only for the cluster with the oxygen vacancy. For pnictides, charge transfer with positive and negative atoms in the FeAs layer is observed in fluorine-doped clusters but not in undoped clusters. For metallic superconductors, alternating positive and negative layers are found in the clusters. These calculated charge distributions are analyzed as a result of electron transfer occurring in the superconducting state involving unsynchronized resonances, as predicted by the RVB theory of Pauling. From this analysis, combinations of chemical elements and their relationship with the superconducting transition temperature are discussed.

Uspekhi Fizicheskih Nauk, 2010

The energy density of a luminous silicon ball [Phys. Rev. Lett. 98 048501 (2007)] is calculated f... more The energy density of a luminous silicon ball [Phys. Rev. Lett. 98 048501 (2007)] is calculated for a model with a metal core surrounded by an atmosphere of silicon oxides. Experimental data combined with the molecular orbital calculations of the oxidation enthalpy lead to a mean energy density of 3.9 MJ m À3 , which is within the range of estimates from other ball lightning models. This result provides a good evidence to support the silicon-based model.

Journal of the Brazilian Chemical Society, 2012

3 O 8.27), de sistemas metálicos (Nb 3 Ge, MgB 2) e do pnictido LaO 0.92 F 0.08 FeAs indicaram a ... more 3 O 8.27), de sistemas metálicos (Nb 3 Ge, MgB 2) e do pnictido LaO 0.92 F 0.08 FeAs indicaram a ocorrência da ressonância não-sincronizada no estado supercondutor, como prevê a teoria RVB (resonating valence bond) de Pauling. Para os cupratos, a ressonância não-sincronizada envolve transferência de elétron entre átomos de Cu, acompanhada pela redução da carga dos átomos La, Sr, Y e Ca. Para o MgB 2 , a transferência de elétron ocorre na camada do Mg, enquanto a do B comporta-se como reservatório de cargas. Para o Nb 3 Ge, a ressonância ocorre entre átomos de Ge, que devem ser os responsáveis pela transferência de carga. Para o LaO 0.92 F 0.08 FeAs, ambas as camadas de La-O e Fe-As estão envolvidas no mecanismo da supercondutividade. A observação de ressonâncias não-sincronizadas nestes sistemas fornece uma evidência em favor da RVB como uma teoria apropriada para a supercondutividade em altas temperaturas (high-T C). DFT calculations performed on different cluster models of cuprates (LaBa 2 Cu 3 O 6.

$Research paper thumbnail of Electronic structure of fractionally nuclear charged atoms$

Journal of the Brazilian Chemical Society, 2008

Diferentes propriedades da química de quarks são estudadas por cálculos ab initio Hartree-Fock em... more Diferentes propriedades da química de quarks são estudadas por cálculos ab initio Hartree-Fock em átomos com carga nuclear fracionária. Os estados fundamental e excitado de átomos de sódio com quarks ligados ao núcleo são obtidos usando cálculos de interação de configuração. Este estudo sugere que a transição eletrônica 2 P 2 S no sódio pode ser usada como guia para observação de quarks não confinados. A variação da energia de ligação eletrônica com a carga nuclear para a série isoeletrônica de átomos com carga nuclear fracionária A ±2/3 e A ±1/3 (A = H, Li, Na, P and Ca) foi analisada. Os cálculos apresentados sugerem, que os quarks não confinados preferem se ligar a núcleos pesados, e que o par quark-antiquark poderia ser estabilizado na presença da matéria atômica. Different properties of quark chemistry are studied by performing accurate ab initio Hartree-Fock calculations on fractionally nuclear charged atoms. Ground and first excited states of sodium atoms with quarks attached to the nucleus are obtained using CI calculations. It is suggested that the sodium 2 P 2 S electronic transition can be used as a guide in searching for unconfined quarks. Also, the variation of the binding electronic energy with nuclear charge in the isoelectronic series of fractionally nuclear charged atoms A ±2/3 and A ±1/3 (A = H, Li, Na, P and Ca) is analyzed. The present calculations suggest that unconfined colored particles have large appetite for heavy nuclei and that quark-antiquark pairs could be stabilized in presence of the atomic matter.

Journal of Geophysical Research, 2009

We describe a mechanism of enhanced terrestrial gamma ray flash production seeding via muon decay... more We describe a mechanism of enhanced terrestrial gamma ray flash production seeding via muon decay in the presence of high electric fields associated with lightning. Our model predicts 10 7 relativistic seed electrons per millisecond at about 15 km altitude with mean energy of 35 MeV and an avalanche multiplication factor of about 10 10 , in good agreement with Monte Carlo simulations.

Journal of Geophysical Research, 2011

International Journal of Quantum Chemistry, 2010

An ná ál li is se e d da a d di is st tr ri ib bu ui iç çã ão o d de e c ca ar rg ga as s a at tô... more An ná ál li is se e d da a d di is st tr ri ib bu ui iç çã ão o d de e c ca ar rg ga as s a at tô ôm mi ic ca as s n no o m mo od de el lo o R RV VB B p pa ar ra a s su up pe er rc co on nd du ut to or re es s M Ma ar rc co on ni i B Be ez ze er rr ra a d da a S Si il lv va a C Co os st ta a R Re ec ci if fe e-P PE E, , B Br ra as si il l F Fe ev ve er re ei ir ro o d de e 2 20 01 10 0 Costa, Marconi Bezerra da Silva. Análise da distribuição de cargas atômicas no modelo RVB para supercondutores / Marconi Bezerra da Silva Costa.-Recife: O Autor, 2010. viii, 122 folhas. il., fig., tab.

Journal of Molecular Modeling, 2016

The infrared spectrum of water observed in sunspots is complex and dense, with bands separated by... more The infrared spectrum of water observed in sunspots is complex and dense, with bands separated by approximately 0.01 cm −1. For top asymmetrical molecules, there is no theoretical approach that allows for the calculation of rotovibrational energy with such precision. Experimentally derived rotovibracional energy levels of water at high temperatures combined with variational calculations have been used for the band assignments. These energy levels are employed to refine the analysis of a small portion of the infrared absorption spectrum. Such procedure has allowed for the identification of additional 55 bands to the 70 already identified as rotovibrational transitions of the water molecule. Our new assignments, which include pure and cross transitions, offer additional evidence of the existence of water on the sun, but above all they illustrate the complexity of the solar spectrum that involves states with higher levels of rotational excitation. Given the conditions on the sun, more molecules of water would occur in excited electronic states, which include apolar and paramagnetic states, generating intense bands in the spectrum. Since there is an analytical solution for the rotovibrational transitions of linear molecules, we were able to identify 16 bands relative to the excited electronic states 1 B 2 and 3 A 1 in the sunspot spectrum. Density functional B3LYP/ AUG-cc-pVTZ calculations of the electric and magnetic dipole are employed to discuss some consequences of the presence of excited states of water in the dynamics of sunspots and solar magnetic field. Keywords 1 B 2 and 3 A 1 states. Infrared sunspots spectrum. Rotovibrational states. Water excited electronic states. Water on the sun

Some properties of quark chemistry are obtained by performing accurate ab initio Hartree-Fock cal... more Some properties of quark chemistry are obtained by performing accurate ab initio Hartree-Fock calculations on fractionally nuclear charged atoms and molecules formed by these atoms. Ground and first excited states of sodium, lithium, beryllium and magnesium atoms with quarks attached to the nucleus are obtained. It is suggested that the electronic transition can be used as a guide in searching for free quarks. The variation of binding electronic energy with nuclear charge in the isoelectronic series of fractionally nuclear charged atoms A and A (A = H, Li, Na, P and Ca) is analyzed. It is found that unconfined colored particles prefer to bind with heavy atoms and that quark-antiquark pairs can be stabilized in presence of the atomic matter.

$Research paper thumbnail of Electronic structure of fractionally nuclear charged atoms$