Paulo Acioli | Northeastern Illinois University (original) (raw)
Papers by Paulo Acioli
CRC Press eBooks, Oct 1, 2005
Journal of Physical Chemistry C, Aug 10, 2018
Results of photoelectron spectroscopy measurements and density functional theory complemented wit... more Results of photoelectron spectroscopy measurements and density functional theory complemented with correction scheme calculations on electron binding energy (EBE) spectra of anionic Al n Mo, n = 3−5 and 7, clusters are presented and analyzed. The analysis points to the important role of dynamical fluxionality and multiplicity of structural forms as contributing factors in the measured spectra. Using the example of Al 4 Mo − as a paradigmatic case, the separate roles of size, structure/symmetry, and composition in evolving the EBE spectra of precursor pure clusters (in this case, Al 4 − and Al 5 −) into those of bimetallic clusters are demonstrated utilizing a new methodology we developed recently (
European Physical Journal D, Dec 1, 2022
American Journal of Physics, Jul 1, 2019
Energy is a concept widely used in all areas of science but its meaning is not completely underst... more Energy is a concept widely used in all areas of science but its meaning is not completely understood. It is a subtle concept and a straightforward definition is not available. There have been many studies on its meaning and on the different metaphors used to describe it. The present work uses a pragmatic approach to mechanical energy and its conservation by using computer simulations inspired on the work of Chabay and Sherwood. We report the results of modifying the calculus based University Physics sequence at Northeastern Illinois University. The modifications include a revision of the laboratory activities adding computer based activities to the more traditional hands on measurements. A more substantial change was the inclusion of mini-research projects that were part of the National Science Foundation-Improving Undergraduate STEM Education (NSF-IUSE) funded project Peer Enhanced Experiential Research in STEM (PEERS). In this manuscript, we discuss a student project that helps us understand energy, energy exchanges, and energy conservation. We discuss how the chosen student project helps in the understanding on how conserving potentials can lead to apparent non-energy conservation. V
Journal of Physical Chemistry C, Jul 26, 2017
Bulletin of the American Physical Society, Mar 17, 2021
The Journal of Physical Chemistry A
In spring 2020, campuses across the world had to adpat its teaching practices due to the COVID-19... more In spring 2020, campuses across the world had to adpat its teaching practices due to the COVID-19 pandemic. Northeastern Illinois University (NEIU) decided to switch all teaching to remote or online teaching with very little notice. During the summer of 2020 NEIU decided that most of the courses would continue this practice, with a few exceptions. Having the summer to prepare, I decided to teach Mechanics I and Modern Physics I using a flipped classroom approach. Lectures are recorded ahead of time using Zoom and the built-in whiteboard for problem solving. Before the lecture a Just-in-Time WarmUp quiz is administered and the results are used fo rthe initial discussion in the scheduled virtual lecture. After the discussion, students move into Zoom breakout rooms for group work on problem solving and conceptual discussions. I will present the successes and challenges of this approach on a Urban campus.
Spiral waves are self-repeating waves that can form in excitable media, propagating outward from ... more Spiral waves are self-repeating waves that can form in excitable media, propagating outward from their center in a spiral pattern. Spiral waves have been observed in different natural phenomena and have been linked to medical conditions such as epilepsy and atrial fibrillation. We used a simple cellular automaton model to study propagation in excitable media, with a particular focus in understanding spiral wave behavior. The main ingredients of this cellular automaton model are an excitation condition and characteristic excitation and refractory periods. The literature shows that fixed excitation and refractory periods together with specific initial conditions generate stationary and stable spiral waves. In the present work we allowed the activation and refractory periods to fluctuate uniformly over a range of values. Under these conditions formed spiral waves might drift, the wave front might break, and in some extreme cases it might lead to a complete breakdown of the spiral pattern.
American Journal of Physics
The appearance of the coronavirus (COVID-19) in late 2019 has dominated the news in the last few ... more The appearance of the coronavirus (COVID-19) in late 2019 has dominated the news in the last few months as it developed into a pandemic. In many mathematics and physics classrooms, instructors are using the time series of the number of cases to show exponential growth of the infection. In this manuscript we propose a simple diffusion process as the mode of spreading infections. This model is less sophisticated than other models in the literature, but it can capture the exponential growth and it can explain it in terms of mobility (diffusion constant), population density, and probability of transmission. Students can change the parameters and determine the growth rate and predict the total number of cases as a function of time. Students are also given the opportunity to add other factors that are not considered in the simple diffusion model.
Journal of Physics B: Atomic, Molecular and Optical Physics, 1999
... LS Costa§, FV Prudente, PH Acioli, JJ Soares Neto and JDM Vianna Núcleo de Fısica Atô... more ... LS Costa§, FV Prudente, PH Acioli, JJ Soares Neto and JDM Vianna Núcleo de Fısica Atômica, Molecular e Fluidos, Instituto de Fısica, Universidade de Brasılia, CP 04455, 70910-900 Brasılia DF, Brazil Instituto de Fısica, Universidade Federal da ... m=1 g ∗ n(xi)gm( ...
Physical Review B Condensed Matter and Materials Physics, 2006
Results of a theoretical and experimental photoelectron spectroscopy ͑PES͒ study of the size evol... more Results of a theoretical and experimental photoelectron spectroscopy ͑PES͒ study of the size evolution of electronic properties of small Mn n − clusters are presented. The agreement between the computed and measured data verifies the validity of the theoretical treatment. The theoretical analysis leads to the first prediction of nanoscale half metallicity and the size-induced transition to it. It also points to the type of experiments ͑spin-polarized PES͒ that will be able to directly verify the predicted phenomenon.
J Am Chem Soc, 2005
Since the discovery of ferrocene (C 5 H 5 ) 2 Fe and determination of its structure, explorations... more Since the discovery of ferrocene (C 5 H 5 ) 2 Fe and determination of its structure, explorations of sandwich and other complexes of metal atoms with organic molecules evolved into a sovereign area (see, for example, ref 1 and citations therein). The ever-growing interest in these complexes stems from their wide-reaching relevance to catalysis, novel magnetic and optical materials, polymers, molecular recognition, and medical and other applications. 1 Among the systems under active current investigation are V n Bz m (Bz ) C 6 H 6 ) complexes. Mass spectrometric 2,3 and ion mobility 3 measurements suggested that they are particularly stable at m ) n-1, n, and n + 1, and that their energetically preferred structures are linear sandwiches of alternating V and Bz units. Computations 3-5 on V n Bz n+1 , n e 3, provided additional support for these structures. Experimental investigations of V n Bz m complexes also include photo-6 and collision-induced 3,6b dissociation; dipole moment measurements; 7 and EPR, 8-10 PES, 11 and IR 9,12,13 spectroscopy. Data obtained in EPR measurements 8-10 on VBz and VBz 2 were used to estimate their magnetic moments as 1µ B . Recent Stern-Gerlach deflection experiments 14 extend the evidence for the magnetic nature of V n Bz n+1 to n e 4.
Phys Rev B, 1996
We present the results of fixed-node diffusion Monte Carlo calculations of jellium surfaces for m... more We present the results of fixed-node diffusion Monte Carlo calculations of jellium surfaces for metallic densities. We used a trial wave function of the Slater-Jastrow type, with the long-range part of the two-body term modified to account for the anisotropy of the system. The one-body term is optimized so that the electronic density from variational and diffusion Monte Carlo calculations agree with each other. The final densities are close to the densities obtained from density-functional calculations in the local-density approximation and the surface energies to the results obtained using the Langreth-Mehl and Perdew-Wang generalized gradient approximation at high densities (rs<=2.07). At low densities (rs>=3.25) they agree with the results of the Fermi-hypernetted-chain calculations. The pair-correlation functions at regions near the surface are tabulated, showing the anisotropy of the exchange-correlation hole in regions of fast-varying densities.
J Phys Chem a, 2003
Structural and electronic properties of neutral and anionic magnesium clusters with 2 to 22 atoms... more Structural and electronic properties of neutral and anionic magnesium clusters with 2 to 22 atoms are studied using gradient-corrected density functional theory. A new scheme for the conversion of the Kohn-Sham eigenenergies into electron binding energies is utilized to compute the difference in the binding energies of the two most external electrons in the anionic clusters. The results are in very good agreement with the data obtained in recent electron photodetachment experiments. The other electronic properties studied include (a) the binding energy, the second difference of the total energies, the HOMO-LUMO gap, and the vertical ionization potential of the neutral clusters; (b) the vertical electron detachment energy of the anionic clusters; and (c) the character of bonding in both the neutral and the anionic clusters. The analysis focuses on the finite-size analogue of the insulator-to-metal transition. The role and manifestation of the finite-size effects are discussed, and some important implications regarding the interpretation of the experimental data are pointed out.
Phys Rev a, 1999
We propose a generalization of the method proposed by Prudente and Acioli ͓Chem. Phys. Lett. 302,... more We propose a generalization of the method proposed by Prudente and Acioli ͓Chem. Phys. Lett. 302, 249 ͑1999͔͒ to compute rovibrational spectra of molecular systems. We present the expressions of the generalized rotating wave function for n-body systems. We discuss the advantages of the current approach over traditional variational methods. We also obtain an important relation for the Euler angles in terms of the Cartesian components of Jacobi vectors, expressions that are needed to compute the matrix elements utilizing the correlation function quantum Monte Carlo method.
The Journal of Chemical Physics, Apr 30, 2003
A new accurate scheme for converting the Kohn-Sham eigenenergies into electron binding energies i... more A new accurate scheme for converting the Kohn-Sham eigenenergies into electron binding energies is formulated. The accuracy of the scheme is illustrated in applications to ten atoms and three molecules.
CRC Press eBooks, Oct 1, 2005
Journal of Physical Chemistry C, Aug 10, 2018
Results of photoelectron spectroscopy measurements and density functional theory complemented wit... more Results of photoelectron spectroscopy measurements and density functional theory complemented with correction scheme calculations on electron binding energy (EBE) spectra of anionic Al n Mo, n = 3−5 and 7, clusters are presented and analyzed. The analysis points to the important role of dynamical fluxionality and multiplicity of structural forms as contributing factors in the measured spectra. Using the example of Al 4 Mo − as a paradigmatic case, the separate roles of size, structure/symmetry, and composition in evolving the EBE spectra of precursor pure clusters (in this case, Al 4 − and Al 5 −) into those of bimetallic clusters are demonstrated utilizing a new methodology we developed recently (
European Physical Journal D, Dec 1, 2022
American Journal of Physics, Jul 1, 2019
Energy is a concept widely used in all areas of science but its meaning is not completely underst... more Energy is a concept widely used in all areas of science but its meaning is not completely understood. It is a subtle concept and a straightforward definition is not available. There have been many studies on its meaning and on the different metaphors used to describe it. The present work uses a pragmatic approach to mechanical energy and its conservation by using computer simulations inspired on the work of Chabay and Sherwood. We report the results of modifying the calculus based University Physics sequence at Northeastern Illinois University. The modifications include a revision of the laboratory activities adding computer based activities to the more traditional hands on measurements. A more substantial change was the inclusion of mini-research projects that were part of the National Science Foundation-Improving Undergraduate STEM Education (NSF-IUSE) funded project Peer Enhanced Experiential Research in STEM (PEERS). In this manuscript, we discuss a student project that helps us understand energy, energy exchanges, and energy conservation. We discuss how the chosen student project helps in the understanding on how conserving potentials can lead to apparent non-energy conservation. V
Journal of Physical Chemistry C, Jul 26, 2017
Bulletin of the American Physical Society, Mar 17, 2021
The Journal of Physical Chemistry A
In spring 2020, campuses across the world had to adpat its teaching practices due to the COVID-19... more In spring 2020, campuses across the world had to adpat its teaching practices due to the COVID-19 pandemic. Northeastern Illinois University (NEIU) decided to switch all teaching to remote or online teaching with very little notice. During the summer of 2020 NEIU decided that most of the courses would continue this practice, with a few exceptions. Having the summer to prepare, I decided to teach Mechanics I and Modern Physics I using a flipped classroom approach. Lectures are recorded ahead of time using Zoom and the built-in whiteboard for problem solving. Before the lecture a Just-in-Time WarmUp quiz is administered and the results are used fo rthe initial discussion in the scheduled virtual lecture. After the discussion, students move into Zoom breakout rooms for group work on problem solving and conceptual discussions. I will present the successes and challenges of this approach on a Urban campus.
Spiral waves are self-repeating waves that can form in excitable media, propagating outward from ... more Spiral waves are self-repeating waves that can form in excitable media, propagating outward from their center in a spiral pattern. Spiral waves have been observed in different natural phenomena and have been linked to medical conditions such as epilepsy and atrial fibrillation. We used a simple cellular automaton model to study propagation in excitable media, with a particular focus in understanding spiral wave behavior. The main ingredients of this cellular automaton model are an excitation condition and characteristic excitation and refractory periods. The literature shows that fixed excitation and refractory periods together with specific initial conditions generate stationary and stable spiral waves. In the present work we allowed the activation and refractory periods to fluctuate uniformly over a range of values. Under these conditions formed spiral waves might drift, the wave front might break, and in some extreme cases it might lead to a complete breakdown of the spiral pattern.
American Journal of Physics
The appearance of the coronavirus (COVID-19) in late 2019 has dominated the news in the last few ... more The appearance of the coronavirus (COVID-19) in late 2019 has dominated the news in the last few months as it developed into a pandemic. In many mathematics and physics classrooms, instructors are using the time series of the number of cases to show exponential growth of the infection. In this manuscript we propose a simple diffusion process as the mode of spreading infections. This model is less sophisticated than other models in the literature, but it can capture the exponential growth and it can explain it in terms of mobility (diffusion constant), population density, and probability of transmission. Students can change the parameters and determine the growth rate and predict the total number of cases as a function of time. Students are also given the opportunity to add other factors that are not considered in the simple diffusion model.
Journal of Physics B: Atomic, Molecular and Optical Physics, 1999
... LS Costa§, FV Prudente, PH Acioli, JJ Soares Neto and JDM Vianna Núcleo de Fısica Atô... more ... LS Costa§, FV Prudente, PH Acioli, JJ Soares Neto and JDM Vianna Núcleo de Fısica Atômica, Molecular e Fluidos, Instituto de Fısica, Universidade de Brasılia, CP 04455, 70910-900 Brasılia DF, Brazil Instituto de Fısica, Universidade Federal da ... m=1 g ∗ n(xi)gm( ...
Physical Review B Condensed Matter and Materials Physics, 2006
Results of a theoretical and experimental photoelectron spectroscopy ͑PES͒ study of the size evol... more Results of a theoretical and experimental photoelectron spectroscopy ͑PES͒ study of the size evolution of electronic properties of small Mn n − clusters are presented. The agreement between the computed and measured data verifies the validity of the theoretical treatment. The theoretical analysis leads to the first prediction of nanoscale half metallicity and the size-induced transition to it. It also points to the type of experiments ͑spin-polarized PES͒ that will be able to directly verify the predicted phenomenon.
J Am Chem Soc, 2005
Since the discovery of ferrocene (C 5 H 5 ) 2 Fe and determination of its structure, explorations... more Since the discovery of ferrocene (C 5 H 5 ) 2 Fe and determination of its structure, explorations of sandwich and other complexes of metal atoms with organic molecules evolved into a sovereign area (see, for example, ref 1 and citations therein). The ever-growing interest in these complexes stems from their wide-reaching relevance to catalysis, novel magnetic and optical materials, polymers, molecular recognition, and medical and other applications. 1 Among the systems under active current investigation are V n Bz m (Bz ) C 6 H 6 ) complexes. Mass spectrometric 2,3 and ion mobility 3 measurements suggested that they are particularly stable at m ) n-1, n, and n + 1, and that their energetically preferred structures are linear sandwiches of alternating V and Bz units. Computations 3-5 on V n Bz n+1 , n e 3, provided additional support for these structures. Experimental investigations of V n Bz m complexes also include photo-6 and collision-induced 3,6b dissociation; dipole moment measurements; 7 and EPR, 8-10 PES, 11 and IR 9,12,13 spectroscopy. Data obtained in EPR measurements 8-10 on VBz and VBz 2 were used to estimate their magnetic moments as 1µ B . Recent Stern-Gerlach deflection experiments 14 extend the evidence for the magnetic nature of V n Bz n+1 to n e 4.
Phys Rev B, 1996
We present the results of fixed-node diffusion Monte Carlo calculations of jellium surfaces for m... more We present the results of fixed-node diffusion Monte Carlo calculations of jellium surfaces for metallic densities. We used a trial wave function of the Slater-Jastrow type, with the long-range part of the two-body term modified to account for the anisotropy of the system. The one-body term is optimized so that the electronic density from variational and diffusion Monte Carlo calculations agree with each other. The final densities are close to the densities obtained from density-functional calculations in the local-density approximation and the surface energies to the results obtained using the Langreth-Mehl and Perdew-Wang generalized gradient approximation at high densities (rs<=2.07). At low densities (rs>=3.25) they agree with the results of the Fermi-hypernetted-chain calculations. The pair-correlation functions at regions near the surface are tabulated, showing the anisotropy of the exchange-correlation hole in regions of fast-varying densities.
J Phys Chem a, 2003
Structural and electronic properties of neutral and anionic magnesium clusters with 2 to 22 atoms... more Structural and electronic properties of neutral and anionic magnesium clusters with 2 to 22 atoms are studied using gradient-corrected density functional theory. A new scheme for the conversion of the Kohn-Sham eigenenergies into electron binding energies is utilized to compute the difference in the binding energies of the two most external electrons in the anionic clusters. The results are in very good agreement with the data obtained in recent electron photodetachment experiments. The other electronic properties studied include (a) the binding energy, the second difference of the total energies, the HOMO-LUMO gap, and the vertical ionization potential of the neutral clusters; (b) the vertical electron detachment energy of the anionic clusters; and (c) the character of bonding in both the neutral and the anionic clusters. The analysis focuses on the finite-size analogue of the insulator-to-metal transition. The role and manifestation of the finite-size effects are discussed, and some important implications regarding the interpretation of the experimental data are pointed out.
Phys Rev a, 1999
We propose a generalization of the method proposed by Prudente and Acioli ͓Chem. Phys. Lett. 302,... more We propose a generalization of the method proposed by Prudente and Acioli ͓Chem. Phys. Lett. 302, 249 ͑1999͔͒ to compute rovibrational spectra of molecular systems. We present the expressions of the generalized rotating wave function for n-body systems. We discuss the advantages of the current approach over traditional variational methods. We also obtain an important relation for the Euler angles in terms of the Cartesian components of Jacobi vectors, expressions that are needed to compute the matrix elements utilizing the correlation function quantum Monte Carlo method.
The Journal of Chemical Physics, Apr 30, 2003
A new accurate scheme for converting the Kohn-Sham eigenenergies into electron binding energies i... more A new accurate scheme for converting the Kohn-Sham eigenenergies into electron binding energies is formulated. The accuracy of the scheme is illustrated in applications to ten atoms and three molecules.