Jorge Morales - Academia.edu (original) (raw)

Papers by Jorge Morales

Past and present coherent-states (CS) efforts with the electron nuclear dynamics (END) theory at ... more Past and present coherent-states (CS) efforts with the electron nuclear dynamics (END) theory at its simplest level (SL-END) are reviewed. END is a time-dependent, variational, non-adiabatic, direct-dynamics method that describes simultaneously the nuclei and electrons of a molecular system. Within that characterization, SL-END adopts a classical-mechanics description for the nuclei and a quantum single-determinantal representation for the electrons. From its very inception, SL-END has been associated with the CS theory. CS sets are continuous and over-complete sets that satisfy the resolution of identity with a positive measure. Different CS sets can play an astonishing number of roles within SL-END that have several practical consequences. Originally, SL-END utilized the canonical and Thouless CS sets to correctly represent the nuclear and electronic parts of the SL-END wavefunction, respectively, thus defining a proper phase space for the SL-END dynamical equations. Later, canoni...

The Journal of Chemical Physics, 2020

We reformulate a previous rotational coherent state (CS) to obtain temporally stable (TS) CSs for... more We reformulate a previous rotational coherent state (CS) to obtain temporally stable (TS) CSs for the spherical rotor (SR) and linear rotor (LR): TSSR and TSLR CSs, respectively. Being TS, the new CSs remain within their own classes during dynamics by evolving exclusively through their CS parameters. The new TS CSs are now appropriate to reconstruct quantum rotational properties from classical-mechanics simulations of chemical reactions. Following literature precedents, we enforce temporal stability by incorporating action-angle-related phase factors into the parameters of the original CS. In addition, to elucidate CS quantum reconstruction procedures, we derive one more rotational CS from a quantum electron nuclear dynamics description of a diatomic rotor (DR). The DR CS and the TSLR CS are not identical but display similar structures and properties. We rigorously demonstrate and examine the key properties of the three CSs: continuity, resolution of unity, temporal stability, actio...

Theoretical Chemistry Accounts, 2020

Electron nuclear dynamics (END) is an ab initio quantum dynamics method that adopts a time-depend... more Electron nuclear dynamics (END) is an ab initio quantum dynamics method that adopts a time-dependent, variational, direct, and non-adiabatic approach. The simplest-level (SL) END (SLEND) version employs a classical mechanics description for nuclei and a Thouless single-determinantal wave function for electrons. A higher-level END version, END/Kohn-Sham density functional theory, improves the electron correlation description of SLEND. While both versions can simulate various types of chemical reactions, they have difficulties to simulate scattering/capture of electrons to/from the continuum due to their reliance on localized Slater-type basis functions. To properly describe those processes, we formulate END with plane waves (PWs, END/PW), basis functions able to represent both bound and unbound electrons. As extra benefits, PWs also afford fast algorithms to simulate periodic systems, parametric independence from nuclear positions and momenta, and elimination of basis set linear dependencies and orthogonalization procedures. We obtain the END/PW formalism by extending the Thouless wave function and associated electron density to periodic systems, expressing the energy terms as functionals of the latter entities, and deriving the energy gradients with respect to nuclear and electronic variables. END/ PW has a great potential to simulate electron processes in both periodic (crystal) and aperiodic (molecular) systems (the latter in a supercell approach). Following previous END studies, END/PW will be applied to electron scattering processes in proton cancer therapy reactions.

Physical Chemistry Chemical Physics, 2019

Low degrees of symmetry breaking in initial states lead to full-blown symmetry breaking and impro... more Low degrees of symmetry breaking in initial states lead to full-blown symmetry breaking and improved predictions in time-dependent direct dynamics.

AIP Conference Proceedings, 2007

Inspired by Ohrn's electron nuclear dynamics (END), a new coherent‐states dynamics (CSD) to s... more Inspired by Ohrn's electron nuclear dynamics (END), a new coherent‐states dynamics (CSD) to study chemical reactions is presented. CSD exploits basic properties of coherent states (CS) sets to represent the electrons and nuclei in a reactive system, and advances the concept of quasi‐classical CS to formulate quantum/classical treatments. An original feature in CSD is its systematic employment of different types of CS to address specific chemical problems; some of those CS have been created by this author. In that context, END is revisited and some modifications are suggested. A full CSD procedure to calculate chemical reaction properties (e.g. differential cross sections) is also introduced in conjunction with semiclassical techniques. Results of simulations and properties calculations of the H++C2H4 and H++CO2 reactive systems at ELab = 30 eV are presented in comparison with experimental data. Current efforts in the CSD project (such as a CSD compute grid implementation and a CSD density‐functional‐theor...

International Journal of Quantum Chemistry, 1997

ABSTRACT The importance of isotopic substitution as a tool for elucidation of chemical reaction e... more ABSTRACT The importance of isotopic substitution as a tool for elucidation of chemical reaction events originates in the fact that the Coulombic Hamiltonian is isotopically invariant except for the nuclear kinetic energy term. Thus, in theories of isotope effects based on the Born-Oppenheimer scheme, the basic presumption is the invariance of the potential energy surface (PES). We use, however, a fully dynamic approach, called Electron Nuclear Dynamics (END), which does not require a preconstructed PES. Since the END formalism is rather different from commonly used procedures, we study the anharmonic nuclear vibration in isotopic species of the HeH+ molecular ion as a model problem. A single time-dependent complex parametrized determinantal wave function is used for the electrons and the nuclei are treated classically. The time evolution of the nuclear and electronic dynamical variables obtained by integration of equations of motion are reported as bond length, nuclear kinetic energy, and Mulliken populations. The molecule vibrates as a classical object. The product of the reduced mass and the square of the vibrational frequency is isotopomer invariant for any common total energy. The difference between the total energy and the nuclear kinetic energy as a function of the internuclear distance is interpreted as the average dynamic potential. © 1997 John Wiley & Sons, Inc.

Chemical Physics Letters, 2012

H + + NO(v i = 0) = H + + NO(v f = 0-2) at E Lab = 30 eV is investigated with the simplest-level ... more H + + NO(v i = 0) = H + + NO(v f = 0-2) at E Lab = 30 eV is investigated with the simplest-level electron nuclear dynamics (SLEND) method. In a direct, time-dependent, variational, and non-adiabatic framework, SLEND adopts nuclear classical mechanics and an electronic single-determinantal wavefunction. A coherentstates (CS) procedure recovers quantum vibrational properties from classical mechanics. Besides canonical CS, SU(1,1), SU(2), and Gazeau-Klauder Morse CS are innovatively introduced to treat anharmonicity. SLEND vibrational differential cross, rainbow scattering angles, and H + energy loss spectra compare well with experimental data and with vibrational close-coupling rotational infinite-order sudden approximation results obtained at a higher computational cost.

Chemical Physics Letters, 2004

Representative fullerene-like phosphorus P n clusters in the range of 14 6 n 6 60 are for the fir... more Representative fullerene-like phosphorus P n clusters in the range of 14 6 n 6 60 are for the first time investigated with density functional theory (DFT) and Hartree-Fock (HF) methods. Total energies, structural properties, binding energies, and HOMO-LUMO gaps of several P n clusters are systematically calculated and discussed. Present results indicate that all the P n clusters found on local energy minima are unstable with respect to dissociation into P 4 molecules, with their stability decreasing almost monotonically with the cluster size in the range of 14 6 n 6 40. In agreement with density functional tight-binding (DFTB) results, P n clusters tend to behave differently from their C n and Si n equivalents as evinced by their decreased stabilities, pentagon-fusion patterns, and more expanded structures.

Revista Argentina de Ciencias del Comportamiento, 2011

En este trabajo rechazo la posibilidad de que el razonamiento animal, en particular la negacion, ... more En este trabajo rechazo la posibilidad de que el razonamiento animal, en particular la negacion, involucre necesariamente la representacion de Ausencia, como sugiere Jose Luis Bermudez, pues esta operaria como una negacion logica (no disponible para criaturas no linguisticas). Experimentos de creencias falsas, fingimiento y comunicacion muestran que animales no humanos (al menos ciertos primates) tienen dificultades para representar entidades o propiedades ausentes. Ofrezco una explicacion alternativa recurriendo a los juicios sub-simbolicos de semejanza propuestos por Vigo & Allen e introduzco la nocion de expectativa: la negacion se da a traves de la incompatibilidad entre una representacion esperada y la actual. Finalmente, sostengo que el paradigma de expectativas puede ser extrapolado a otros experimentos en psicologia cognitiva (tanto con ninos prelinguisticos como con animales) para disenar experimentos ―justos‖ que examinen otras mentes considerando sus habilidades reales. A...

The Journal of chemical physics, Jan 14, 2011

The H(+) + N(2) system at E(Lab) = 30 eV, relevant in astrophysics, is investigated with the simp... more The H(+) + N(2) system at E(Lab) = 30 eV, relevant in astrophysics, is investigated with the simplest-level electron nuclear dynamics (SLEND) method. SLEND is a time-dependent, direct, variational, non-adiabatic method that employs a classical-mechanics description for the nuclei and a single-determinantal wavefunction for the electrons. A canonical coherent-states procedure, intrinsic to SLEND, is used to reconstruct quantum vibrational properties from the SLEND classical mechanics. Present simulations employ three basis sets: STO-3G, 6-31G, and 6-31G∗∗, to determine their effect on the results, which include reaction visualizations, product predictions, and scattering properties. Present simulations predict non-charge-transfer scattering and N(2) collision-induced dissociation as the main reactions. Average vibrational energy transfer, H(+) energy-loss spectra, rainbow angle, and elastic vibrational differential cross sections at the SLEND∕6-31G∗∗ level agree well with available e...

The Journal of chemical physics, Jan 7, 2012

The astrophysically relevant system H(+) + CO (v(i) = 0) → H(+) + CO (v(f)) at E(Lab) = 30 eV is ... more The astrophysically relevant system H(+) + CO (v(i) = 0) → H(+) + CO (v(f)) at E(Lab) = 30 eV is studied with the simplest-level electron nuclear dynamics (SLEND) method. This investigation follows previous successful SLEND studies of H(+) + H(2) and H(+) + N(2) at E(Lab) = 30 eV [J. Morales, A. Diz, E. Deumens, and Y. Öhrn, J. Chem. Phys. 103(23), 9968 (1995); C. Stopera, B. Maiti, T. V. Grimes, P. M. McLaurin, and J. A. Morales, J. Chem. Phys. 134(22), 224308 (2011)]. SLEND is a direct, time-dependent, variational, and non-adiabatic method that adopts a classical-mechanics description for the nuclei and a single-determinantal wavefunction for the electrons. A canonical coherent-states (CS) procedure associated with SLEND reconstructs quantum vibrational properties from the SLEND classical dynamics. Present SLEND results include reactivity predictions, snapshots of the electron density evolution, average vibrational energy transfers, rainbow angle predictions, total and vibrational...

Physical Chemistry Chemical Physics, 2020

Canonical coherent states accurately reconstruct quantum state-to-state vibrational properties fr... more Canonical coherent states accurately reconstruct quantum state-to-state vibrational properties from classical-mechanics normal modes in electron nuclear dynamics simulations.

We report our ongoing implementation of the electron nuclear dynamics (END) theory as a multi dom... more We report our ongoing implementation of the electron nuclear dynamics (END) theory as a multi domain grid service involving Globus toolkit, Avaki compute grid, and Avaki data grid. END provides a genuine quantum dynamics but recast in a generalized classical Hamiltonian format via coherent states (CS) parameterization. END simulations of chemical reactions demand several trajectory calculations in quantum phase space and naturally call for a grid solution. The current grid implementation is based on the suite of programs CSTechG, which has been tested for various architectures under different conditions involving file staging and several queuing techniques. Different components and services of the application and sample calculations for the + H CH CH + ≡ reaction system are also presented.

Chemical Physics Letters, Mar 1, 2006

We present a combined coherent states (CS)/density functional theory approach to molecular dynami... more We present a combined coherent states (CS)/density functional theory approach to molecular dynamics within the electron nuclear dynamics framework. Nuclei are described by a product of narrow, frozen Gaussian wave packets that is approximately separable into ...

Chemical Physics, 2003

Clusters of the type Cu n N 0;AE1 (n ¼ 1-4) are investigated computationally using density functi... more Clusters of the type Cu n N 0;AE1 (n ¼ 1-4) are investigated computationally using density functional theory methods. Equilibrium geometries are optimized under the constraint of well-defined point-group symmetries at the B3LYP level employing a pseudo-potential method in conjunction with double-zeta basis sets. In this article, different molecular properties such as total energies, electron affinities, ionization potentials, fragmentation energies and equilibrium geometries of the Cu n N 0;AE1 (n ¼ 1-4) clusters are systematically calculated and discussed. In particular, the photoelectron spectra of the anionic Cu n N À1 (n ¼ 2-4) clusters are calculated showing a good agreement with the available experimental results. In addition, Mulliken and natural orbital population analyses, and natural orbital configurations are calculated in order to elucidate the charge distributions in the clusters.

Chemical Physics Letters, Oct 1, 2005

ABSTRACT Preliminary results of an exhaustive study of H+ + HCCH at ELab = 30 eV within the elect... more ABSTRACT Preliminary results of an exhaustive study of H+ + HCCH at ELab = 30 eV within the electron nuclear dynamics (END) and coherent state dynamics (CSD) theories are herein presented. Current END–CSD method employs frozen Gaussian wave packets in the semiclassical limit of ℏ → 0 for the nuclei and a single-determinantal Thouless coherent state (CS) for the electrons. The simulated 6800 trajectories from 68 independent HCCH target orientations provide a definite description of all the reactive processes, including H2 formation and charge transfers. Differential and integral cross-sections are evaluated via a novel CS S-matrix formulation in conjunction with semiclassical techniques. Calculated cross-sections show a good agreement with both experimental and previous END results.

The H CF4 reaction at collision energies ELab 20 and 30 eV is investigated with the electron nucl... more The H CF4 reaction at collision energies ELab 20 and 30 eV is investigated with the electron nuclear dynamics (END) theory. The level of END herein employed prescribes a classical-mechanics description for the nuclei and a singledeterminantal representation for the electrons. The results include visualizations of the simulated collisions, and calculations of various scattering properties. The present simulations always predict noncharge-transfer scattering (NCTS) for H CF4 and exclude charge-transfer, dissociation, and rearrangement reactions. The predicted rainbow angles and the total NCTS differential cross sections agree satisfactorily with the available experimental results. The present results are compared with those of the previously simulated H CH4. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem 109: 3026–3035, 2009

Journal of Molecular Structure: THEOCHEM, 2003

A systematic theoretical study on the Si n (n ¼ 26-36, 60) cages using semiempirical methods is h... more A systematic theoretical study on the Si n (n ¼ 26-36, 60) cages using semiempirical methods is herein presented. Equilibrium geometries, harmonic vibrational frequency analyses, enthalpies of formations, HOMO-LUMO energy gaps and other properties are calculated at the level of the AM1 theory. Present theoretical results show that all the Si n (n ¼ 26-36, 60) cage isomers exhibiting maximum symmetry undergo slight distortions into more stable structures of lower symmetry. No simple function for the clusters stability with respect to the number of Si atoms can be discerned in the whole Si n (n ¼ 26-36, 60) series. However, the stability in the Si n (n ¼ 33-36) series decreases as the number of Si atoms drops whereas the Si n (n ¼ 26-32) series shows the same trend with the exception of n ¼ 28 and 31. Several instances of four-fold coordinated, distorted sp 3 hybridized Si atoms carrying large net charges have been detected. Calculated HOMO-LUMO energy gaps of these Si n cages lie in the range of 3.9-4.6 eV, being larger than those of both smaller Si n clusters and bulk Si. Comparison with available theoretical and experimental data give firm support to the present application of semiempirical methods to large Si n clusters.

The first systematic study of the TiðH2OÞ n ðn 1⁄4 1–5Þ series of clusters is herein presented at... more The first systematic study of the TiðH2OÞ n ðn 1⁄4 1–5Þ series of clusters is herein presented at the level of the DFT B3LYP method in conjunction with electron core potential basis sets. The investigated structures are relevant for laser-induced and laser-ablation syntheses of titanium compounds, and also for fundamental spectroscopy studies of metal-bearing species in the gas phase. Calculated properties include optimal geometries, total energies, bond lengths, bond angles, natural orbital population analysis charges, and hydration dissociation energies inter alia. Present results reveal a strict correlation between the clusters total energy and their spin state. Without exception, the most stable neutral (cation) clusters TiðH2OÞ 1–5 1⁄2TiðH2OÞ 1þ 1–5 are those with spin state S = 1 (S = 3/2). Comparisons with a few available theoretical results show good agreement. 2005 Elsevier B.V. All rights reserved.