Patricia regina pereira Barreto

Patricia regina pereira Barreto
National Institute for Space Research, Brazil | inpe · Laboratório Associado de Plasma (LAP)

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Publications

Publications (80)
Article
Full-text available
The analytical representation of intermolecular interactions combines dynamical and structural viewpoints, utilizing a spherical harmonics expansion based on high-level ab initio generated stereodirected configurations. The potential energy surface of the H2⋯F2 system is built by a number of selected cuts (leading configurations); the best fits of...
Preprint
Full-text available
Propylene oxide is one of the simplest organic chiral molecules and has attracted considerable interest from the scientific community a few years ago, when it was discovered in the interstellar medium. Here, we report a preliminary study on the interaction between propylene oxide and rare-gas atoms, specifically He, Ne, and Ar. The interaction pote...
Article
Full-text available
We perform a study of the molecular anisotropy for the H2⋯H2 van der Waals system using a spherical harmonics expansion. We use six leading stable configurations to construct our analytical potential energy surface (PES) from ab initio calculations guided qualitatively by the symmetry-adapted perturbation theory (SAPT) analyses. We extrapolate the...
Preprint
Full-text available
The representation of the potential energy surfaces of atom molecule or molecular dimers interactions should account faithfully for the symmetry properties of the systems, preserving at the same time a compact analytical form. To this aim, the choice of a proper set of coordinates is a necessary precondition. Here we illustrate a description in ter...
Chapter
Propylene oxide is one of the simplest organic chiral molecules and has attracted considerable interest from the scientific community a few years ago, when it was discovered in the interstellar medium. Here, we report a preliminary study on the interaction between propylene oxide and rare-gas atoms, specifically He, Ne, and Ar. The interaction pote...
Article
In this work, we present the reaction rate and dissociation of formaldehyde H2CO, where we found three possible pathways for the singlet state (¹A), and two for triplet state (³A). The optimized geometries and frequencies were determined at B3LYP/6-311g(2d,d,p) internal to CBS-QB3 methods. The reaction rates are calculated using the APUAMA code, ap...
Article
Ab initio density functional theory calculations were performed to investigate the mechanism of the reaction of the ethanol with water. The optimization of the geometries and frequencies of reactants, transition states and products of the PES were performed using B3LYP, M06-2X and M08-HX methods. The results were employed to calculate the rate cons...
Article
The \(\hbox {CN} + \hbox {H}_{2}\) reaction was investigated by considering the two possible channels, \(\hbox {H} + \hbox {HCN}\) and \(\hbox {H} + \hbox {HNC}\), taking into account the isotopic effects and with the vibrationally excited states. The frequencies and structures for all species of the \(\hbox {CN} + \hbox {H}_{2}/\hbox {D}_{2}\) rea...
Article
Full-text available
In the present work, the kinetic mechanism of the reaction is studied. The rate constants were determined using the Master Equation Solver for Multi‐Energy Well Reactions (MESMER). The master equation modeling was also employed to examine the pressure dependence for each pathway involved. The theoretical analysis shows that the overall rate coeffic...
Conference Paper
Full-text available
The observation of propylene oxide, one of the simplest organic chiral molecules, in the interstellar space rep-resents a remarkable discovery for the astrochemistry community. In this work, we report the study of the full anisotropic interaction between helium and propylene oxide through both a quantum chemical and a phenomenological approach. Thi...
Chapter
The discovery of propylene oxide in the interstellar medium has raised considerable interest about this molecule, which represents one of the simplest cases of chiral systems. In this paper, we present a quantum chemical study and a phenomenological approach, through the Pirani potential function, of the system He – propylene oxide in fourteen diff...
Article
Rate constants for the Boudouard reactions: CO + CO → CO2 + C and CO + CO → C2O + O, involving ground and vibrationally excited states for both singlet–singlet and singlet–triplet reactant CO molecules, have been obtained by using the transition-state theory on an ab initio generated potential energy surface. The dependence of the activation energi...
Article
Full-text available
We present a theoretical study on the detailed mechanism and kinetics of the H + HCN → H + HNC process. The potential energy surface was calculated at the complete basis set quantum chemical method, CBS-QB3. The vibrational frequencies and geometries for four isomers (H 2CN, cis-HCNH, trans-HCNH, CNH 2), and seven saddle points (TSn where n = 1 − 7...
Article
The spherical-harmonics expansion is a mathematically rigorous procedure and a powerful tool for the representation of potential energy surfaces of interacting molecular systems, determining their spectroscopic and dynamical properties, specifically in van der Waals clusters, with applications also to classical and quantum molecular dynamics simula...
Article
The addition of C2 to HCN is of relevant interest in astrochemistry. We studied the pathways of this addition to produce CCCN and estimated its reaction rate using the Master Equation in the circumstellar environment. From the results of this study, it was possible to show that a different pathway in the Surface Potential Energy-PES can also be inv...
Article
Full-text available
APUAMA is a free software designed to determine the reaction rate and thermodynamic properties of chemical species of a reagent system. With data from electronic structure calculations, the APUAMA determine the rate constant with tunneling correction, such as Wigner, Eckart and small curvature, and also, include the rovibrational level of diatomic...
Conference Paper
The representation of the potential energy surfaces of atom-molecule or molecular dimers interactions should account faithfully for the symmetry properties of the systems, preserving at the same time a compact analytical form. To this aim, the choice of a proper set of coordinates is a necessary precondition. Here we illustrate a description in ter...
Article
For the prototypical diatomic-molecule-diatomic-molecule interactions H2-HX and H2-X2, where X = F, Cl, Br, quantum chemical ab initio calculations are carried out on grids of the configuration space, which permit a spherical-harmonics representation of the potential energy surfaces (PES). Dimer geometries are considered for sets of representative...
Article
A study of the umbrella motion of the methyl cation, radical, and anion molecules is presented. This is the floppiest mode of vibration of all three species and its characterization is of fundamental importance for understanding their reactivity. Minimum Energy Paths of the umbrella motions according to the hyperspherical treatment were obtained, b...
Article
The main purpose of the present work is to characterize the umbrella inversion motion of the CH-3, CH3 and CH-3 molecules as a function of the environmental conditions. In particular, for the three investigated species we have studied how temperature affects times for umbrella inversion modes and their propagation velocity. These data are used to p...
Article
Full-text available
In this work, we show a new Potential Energy Surface (PES) for the He3 complex. The PES was obtained using hyperspherical coordinates. The potential employed has a well defined and very simple analytical form. The radial dependence was obtained by considering three "leading" configurations whose energies, computed at CCSD(T) and MRCI levels and six...
Conference Paper
Full-text available
The interaction energy of the H2O⋯X2 complexes, with X = H, N and F has been analyzed by using the SAPT (Symmetry Adapted Perturbation Theory) methodology. The decomposition of the interaction energy into distinct physical components is a unique feature of SAPT which distinguishes this method from the super molecular approach. In SAPT, the interact...
Conference Paper
An extensive quantum chemical study of the potential energy surface (PES) for the different pathways of the reaction of CN + C2H4 is reported. Critical geometries of this reaction were optimized at M06L and CCSD/Aug-cc-pVDZ levels of theory. The theoretical rate constants are also calculated for the main reaction pathway using the transition state...
Article
Full-text available
A representation, based on the hyperspherical harmonics expansion, is given for the potential energy surfaces for the interactions of H2O with H2, N2 and O2. The interaction energies have been obtained by extensive ab initio calculations at the CCSD(T)/aug-cc-pVTZ level. The results are compared with available experimental information and with prev...
Article
This article is an account and extension of a series of recent investigations, which using extensive quantum chemical methods provide analytical hyperspherical representations of the potential energy surfaces for the interactions of rare gases with H2S as a rigid molecule, and H2S2, considered as a floppy molecule with respect to torsional mode. Fo...
Conference Paper
In this work we are concerned with a description of the fourteen low-lying doublet and quartet electronic states of the MgCl molecule correlate to the two lowest dissociation channels. The first two states (X) 2Sigma+ and (1) 2Pi correlate to the first dissociation channel, Mg (1Sg) + Cl (2Pu), and the other twelve states correlate to the second ch...
Conference Paper
In this work is presented, for the first time, an accurate identification of the Einstein coefficients and lifetimes for the band system (1) 3Pi-(X) 3Sigma- of the CaSi molecule. We also are mainly concerned with an accurate spectroscopic characterization of the lowest-lying states of CaSi molecule. These states correlate with the four lowest disso...
Article
Full-text available
Cited By (since 1996): 1, Export Date: 29 June 2012, Source: Scopus, Art. No.: 028111, CODEN: PHSTB, doi: 10.1088/0031-8949/84/02/028111, Language of Original Document: English, Correspondence Address: Barreto, P.R.P.; Instituto Nacional de Pesquisas Espaciais (INPE)/MCT, Laboratòrio Associado de Plasma (LAP), São José dos Campos, SP, CEP 12247-...
Article
In this work we analyzed the multiple channels of the reaction NF+F through the evaluation of thermal rate constants with both Wigner and Eckart tunneling corrections. Minimum energy paths and intrinsic reaction coordinates of the systems were obtained and accurately studied in order to ensure the consistency of our results. Specifically, we invest...
Article
In this work, we discuss the representation in different orthogonal coordinates sets of highly symmetric P4 molecule whose equilibrium configuration is tetrahedral. For this purpose, the H (or diatom–diatom) and Wigner orthogonal representations are used to study the singlet (ground) electronic state of the title molecule, whereas the V (or diatom–...
Chapter
Full-text available
FOR CITATION: D.C. Barbosa et al. Diamond Nanostructures Growth. Encyclopedia of Nanoscience and Nanotechnology. Edited by Hari Singh Nalwa. American Scientific Publishers, 2011, v. 13, p. 59-78. ISBN: 1-58883-162-0
Conference Paper
This work studied the role of argon insertion in diamond deposition using a Hot Filament Chemical Vapour Deposition (HFCVD) system and a gas mixture of methane and hydrogen. The mixture of methane and hydrogen was fixed in 2 and 10 vol.%. The argon content varied for the values of 5, 15, 30, 45, 60, 75 and 90 vol.%. Substrate temperature was 750 ºC...
Article
Diamond with different grain sizes and nanographite films were grown on silicon and diamond substrate using 90 vol.% argon in hydrogen and methane gas mixtures by hot filament chemical vapor deposition method (HFCVD). In current study, the methane volume concentration was varied from 0.125 to 2 vol. % in order to estimate its effect on film morphol...
Article
Transition State Theory, with Wigner tunneling correction, was employed to determine the thermal rate coefficients for the first excited state of the H+ + LiH reaction using the potential energy surface calculated and fitted by Martinazzo et al. [Martinazzo et al., J Chem Phys 2003, 119, 11241]. The calculated thermal rate coefficients, in the temp...
Article
This study is intended as a continuation of previous experimental and theoretical works on the systems H2O-Rg, H2S-Rg, H 2O2-Rg, and H2S2-Rg, where Rg = He, Ne, Ar, Kr, Xe. For the H2O-Rg and H2S-Rg systems, molecular and atomic polarizabilities have been calculated and from them, using phenomenological correlation formulas modeling the dispersion-...
Article
In order to describe the umbrella inversion mode, which is characteristic of AB(3)-type molecules, we have introduced an alternative hyperspherical coordinate set based on a parametrization of Radau-Smith orthogonal vectors and have considered constraints which allow us to enforce the C(3v) symmetry. Structural properties and electronic energies at...
Article
We have theoretically studied the NF(3) = NF(2) + F, NF(2) + F = NF + F(2), and NF(2) + F = NF(2) + F reactive processes. More precisely, we have evaluated the thermal rate constants (TRC), with the Wigner and Eckart tunneling corrections, minimum energy path, and the intrinsic reaction coordinates of these systems. The NF(3) = NF(2) + F convention...
Article
In the present paper, we introduce a representation of the potential energy surface for the H(2)O...H(2) system based on orthogonal vectors, assuming that the two molecules are rigid. We represent the interaction potential by an expansion in real hyperspherical harmonics depending on the distance between the centers of mass of the two molecules and...
Article
Full-text available
The structural and energetic properties of the H(2)S(2) molecule have been studied using density functional theory, second-order Moller-Plesset method, and coupled cluster theory with several basis sets. In order to extend previous work on intra- and intermolecular dynamics of the chirality changing modes for H(2)O(2) and its derivatives, our focus...
Article
Este trabalho é calculada o potencial de interação entre o H2 O2 e H2 S2 com os gases nobres, He, Ne, Ar, Kr, e Xe. O peróxido e persulfeto de hidrogênio foram modelados como moléculas rígidas, exceto pelo modo torsional ao londo da ligação X-X, com X = O ou S. A maior preocupação foi a definição do sistema de coordenadas e a expansão nos harmônico...
Article
A quantum chemical exploration is reported on the interaction potentials of H2O2 with the rare gases, He, Ne, Ar, Kr, and Xe. Hydrogen peroxide (the simplest example of chiral molecule in its equilibrium geometry) is modeled as rigid except for the torsional mode around the O-O bond. However, on the basis of previous work (Maciel, G. S.; et al. Che...
Article
Full-text available
Integral cross sections for collisions of rotationally hot H2S molecules with rare gas atoms (Ne, Ar, and Kr) have been measured, in the collision energy range of 10-60 kJ mol(-1), using a molecular beam apparatus operating under high resolution both in angle and in velocity. A well resolved glory pattern has been measured which permitted the accur...
Article
Full-text available
In this paper we compare semiclassical initial value representation, conventional transition state theory with Wigner and Eckart tunneling correction, quantum reduced dimensionality, and quasiclassical thermal rate coefficients for N+N(2) exchange reaction.
Article
In this work, we present the rate constants, with the Wigner and Eckart tunneling corrections and the minimum energy path calculated with our own code for the NF3 + N = NF2 + NF gas-phase reaction, over the temperature range of 200-4000 K. The information about equilibrium geometries, frequencies and the potential energies for reactant, products an...
Article
In this work, we present the H2O interaction with H2O, (H2O)2 and CO molecules using ab initio calculation combined with both supermolecular and multipolar expansion methods. Molecular structures and electronic properties of monomers were calculated with MP2/6-311++G(3d,3p) level. The interaction energy for the H2O dimer, trimer and H2O⋯CO complex...
Article
In this work, we present the H 2 O interaction with H 2 O, (H 2 O) 2 and CO molecules using ab initio calculation combined with both supermolecular and multipolar expansion methods. Molecular structures and electronic properties of monomers were calculated with MP2/6-311++G(3d,3p) level. The interaction energy for the H 2 O dimer, trimer and H 2 OÁ...
Article
A kinetic mechanism was developed for the growth of boron nitride films, including up to 35 species and 1012 gas-phase reac-tions. For 117 elementary reactions, rate constants are available from published experimental/theoretical data and a code was writ-ten to estimate the others using transition state theory. As an example of our approach, we rep...
Article
Full-text available
Cited By (since 1996): 10, Export Date: 29 June 2012, Source: Scopus, CODEN: CHPLB, doi: 10.1016/j.cplett.2005.07.041, Language of Original Document: English, Correspondence Address: Barreto, P.R.P.; Instituto de Física, Universidade Brasília, CP04455, Brasília, DF, CEP 70919-970, Brazil; email: patricia@plasma.inpe.br, References: Badzian, A.,...
Article
Full-text available
Cited By (since 1996): 14, Export Date: 29 June 2012, Source: Scopus, CODEN: IJQCB, doi: 10.1002/qua.20581, Language of Original Document: English, Correspondence Address: Barreto, P.R.P.; Laboraório Associado de Plasma, Instituto National de Pesquisas Espaciais (INPE), MCT, CP515, S. Jose dos Campos, CEP 12247-970, Brazil; email: patricia@plasma....
Article
Detailed dynamical properties and reaction rate calculations for the ground-state Na + HF -> NaF + H reaction are carried out using two different potential energy surfaces (PES): generalized simulated annealing PES (GSA PES) and bond order 5 PES (1305 PES). These studies show that the quality and efficacy of the GSA PES are comparable to the best P...
Article
A self-consistent set of thermochemical data for 88 chemical species in the B/F/H/N system is obtained from ab initio electronic structure calculation. Calculations were performed for both stable and radical species. The quantities calculated include the atomization energy (∑ D0), heat of formation (ΔHf) at 0 K and 298.15 K, and bond dissociation e...
Article
We developed a simple program to determine the reaction rate by using conventional transition state theory with the Wigner transmission coefficient and also the thermodynamic properties of the species. The hydrogen abstraction in the reaction NH3+H→NH2+H2 is used as a model to demonstrate the program usage. The rate constants have been computed for...
Article
Full-text available
A mechanism is presented for the gas-phase chemistry and surface reactions describing the growth of boron nitride films. The gas phase mechanism includes 33 species and 216 elementary reactions. Rate parameters for 117 elementary reactions were obtained from published experimental/theoretical data and those for the other 99 were determined using tr...
Article
A mechanism is presented for the gas-phase chemistry and surface reactions describing the growth of boron nitride films. The model is applied to films grown using arcjet plasma sources operating on mixtures of Ar, BF^3, H^2 and N^2. The gas-phase kinetic mechanism is comprised of twenty-six species with sixty-seven elementary reactions. A compariso...
Article
In this work measurements of the arc rotation in a low-power plasma torch are described. The torch which is being developed for diamond synthesis operates with Ar/H2 mixtures at total pressures inside the expansion vessel of less than 5000 Pa and currents up to 14 A. A specific four-sectors anode arrangement was developed to measure the arc rotatio...
Conference Paper
Full-text available
This paper discribes the present situation of construction of the ETE Spherical Tokamak presently under development at LAP/INPE.
Article
This report presents the results of the initial characterization of a plasma jet projected for diamond thin film deposition. The temperature and density profiles were measured with a double electrostatic probe. A conceptual project involving the design of a new plasma jet based on gas dynamic theory is also discussed.
Article
Cited By (since 1996): 5, Export Date: 29 June 2012, Source: Scopus, CODEN: JPCAF, doi: 10.1021/jp906415m, Language of Original Document: English, Correspondence Address: Peixoto Bitencourt, A. C.; Centro de Formação de Professores, Universidade Federal do Recôncavo da Bahia (UFRB)Brazil; email: ana.bitencourt@gmail.com, References: Aquilanti, V...
Article
Export Date: 29 June 2012, Source: Scopus, doi: 10.1016/j.comptc.2011.12.024, Language of Original Document: English, Correspondence Address: Barreto, P.R.B.; Instituto Nacional de Pesquisas Espaciais (INPE)/MCT, Laboratòrio Associado de Plasma (LAP), São José dos Campos, SP, CEP 12247-970, CP515, Brazil; email: patricia@plasma.inpe.br, Referenc...
Article
Cited By (since 1996): 16, Export Date: 29 June 2012, Source: Scopus, Art. No.: 164302, CODEN: JCPSA, doi: 10.1063/1.2994732, Language of Original Document: English, Correspondence Address: MacIel, G. S.; Dipartimento di Chimica, Universit̀ di Perugia, Perugia 06123, Italy; email: ciete@dyn.unipg.it, References: Ribó, J.M., Crusats, J., Sagues, F...
Article
Cited By (since 1996): 11, Export Date: 29 June 2012, Source: Scopus, CODEN: CHPLB, doi: 10.1016/j.cplett.2006.06.040, Language of Original Document: English, Correspondence Address: Barreto, P.R.P.; Laboratório Associado de Plasma - LAP, Instituto Nacional de Pesquisas Espaciais - INPE, MCT, CP515, Sao Jose dos Campos, SP CEP, Brazil; email: patr...
Article
Neste trabalho sao apresentados os detalhes de projeto e construcao de um equipamento de tocha de plasma gerada por uma descarga em arco de baixa potencia, 300 - 2000W, para sintetizacao de filmes de diamantes ""CVD"", assim como sao comentados os resultados da caracterizacao do arco eletrico, da tocha de plasma e dos filmes produzidos. O sistema f...