Xavier Giménez | Universitat de Barcelona (original) (raw)
Papers by Xavier Giménez
Journal of Molecular Structure-Theochem, 2005
Physical Chemistry Chemical Physics, 2002
An approximate, computationally feasible expression for the rate constant is derived in terms of ... more An approximate, computationally feasible expression for the rate constant is derived in terms of a generalized formulation of the reaction path Hamiltonian, plus a distributed gaussian expansion scheme to the solution of the Liouville equation for the phase space distribution function. ...
Journal of Molecular Structure-Theochem, 2005
Web of Science® Times Cited
Physical Chemistry Chemical Physics, 2002
An approximate, computationally feasible expression for the rate constant is derived in terms of ... more An approximate, computationally feasible expression for the rate constant is derived in terms of a generalized formulation of the reaction path Hamiltonian, plus a distributed gaussian expansion scheme to the solution of the Liouville equation for the phase space distribution function. ...
The Journal of Chemical Physics, 2004
The coherent-state wave packet dynamics of several model systems is analyzed in terms of Bohm&... more The coherent-state wave packet dynamics of several model systems is analyzed in terms of Bohm's total potential. The quantum dynamics has been obtained by solving the time-dependent Schrodinger equation, and a method for obtaining the total potential from it, involving just matrix algebra, has been proposed. Contrary to what one may expect, it is shown that the time- and state-dependent features of the total potential admit a rationale, classical-like description of quantum effects, leading to a unified picture of them, which is not critically dependent, as for the key features, on the classical potential. An outstanding feature is found to be the relation of the state system's density amplitude and sharpness (in its dependence with position) with quantum effects. Sharp density profiles and low densities cause the total potential to strongly depart from the classical value, in both time regimes and position ranges, which provide a clearer, more deterministic view to quantum dynamics. Free motion as well as scattering processes by square and Eckart barriers have been analyzed by means of careful inspection of several time dependent snapshots. The result is an insightful picture of processes involving tunneling and antitunneling, including their dynamical variants, as well as resonances and quantization.
The Journal of Chemical Physics, 2002
A reaction path Hamiltonian is formulated in terms of a Newton reference path. The defining diffe... more A reaction path Hamiltonian is formulated in terms of a Newton reference path. The defining differential equation for the latter is solved by quadratically expanding the original equation, which in turn leads to an improved formulation of the reaction path Hamiltonian. This new reference ...
A Density Functional View, 2009
Chemical Physics Letters, 1991
... 3. Results of an extended 280 00092614 91 03.50 1991 Elsevier Science Publishers BV (NorthHol... more ... 3. Results of an extended 280 00092614 91 03.50 1991 Elsevier Science Publishers BV (NorthHolland) Parallel calculations of approximate 3D quantum cross sections: the Li + HF reaction Antonio Lagana, Xavier Gimenez Ernesto Garcia 2 ... Walkerand EF Hayes, J. Phys.Chem ...
Journal of Molecular Structure: THEOCHEM, 1988
ABSTRACT The ground state potential energy surface for the reaction on the title has been calcula... more ABSTRACT The ground state potential energy surface for the reaction on the title has been calculated at the UHF-MP3 level and built up by means of a spline procedure. The quantum reactive probabilities for the reaction obtained from hyperspherical calculations show a strong oscillatory behaviour and a number of sharp resonances.
Lecture Notes in Computer Science, 2005
Journal of Molecular Structure-theochem - J MOL STRUC-THEOCHEM, 1999
Extensive theoretical quantum-mechanical calculations are reported for the cross-section and rela... more Extensive theoretical quantum-mechanical calculations are reported for the cross-section and related dynamical quantities of the B+OH→BO+H reaction, on a previously developed potential-energy surface (PES) describing the ground electronic state. These calculations show, as an outstanding feature, the presence of marked structures in the shape of the excitation function as a consequence of the existence of a dense spectrum of rather long-lived resonance states. These are narrow enough to survive the angular momentum averaging, thanks to an important stabilization caused by an electronic minimum corresponding to a linear HOB configuration. The centrifugal barriers due to high values of the orbital angular momentum are found to lead to several orbiting shape resonances, as revealed by the opacity function plots and the dependence of the reaction probability on energy. Differential cross-sections corresponding to energies lying at either reactivity peaks or valleys in the integral cross...
The Journal of Physical Chemistry A, 1997
ABSTRACT In this Letter are presented three-dimensional quantum mechanical cross sections for the... more ABSTRACT In this Letter are presented three-dimensional quantum mechanical cross sections for the title reaction, as calculated for the ab initio potential energy surface of Urban, Jaquet, and Staemmler. The calculations were done within the coupled-states approximation. It is shown that not only are the J = 0 probabilities affected by numerous sharp resonances but even the energy-dependent cross sections, for which such resonances are expected to be smoothed out, are characterized by a rich resonance structure. This is the first time that such oscillatory integral cross sections have been obtained for a chemical exchange process. From comparison with quasi-classical-trajectory results, it is shown that the reaction is dominated by quantum effects to the extent that the quasi-classical-trajectory calculations sometimes become irrelevant.
… Theoretica Chimica Acta …, 1991
Summary Reactive Infinite Order Sudden Approximation calculations have been performed using a com... more Summary Reactive Infinite Order Sudden Approximation calculations have been performed using a computational procedure restructured to run on parallel computers. Computationally intensive sections of the code are analyzed and speedups obtained from a parallel ...
The Journal of Physical …, 1993
Extended approximate three-dimensional quantum calculations of the cross section and product vibr... more Extended approximate three-dimensional quantum calculations of the cross section and product vibrational distributions of the H+ F2-HF+ F reaction have been performed in order to carry out a comparison with existing information. It has been found that our calculations ...
Chemical Physics Letters, 1995
Journal of Molecular Structure-Theochem, 2005
Physical Chemistry Chemical Physics, 2002
An approximate, computationally feasible expression for the rate constant is derived in terms of ... more An approximate, computationally feasible expression for the rate constant is derived in terms of a generalized formulation of the reaction path Hamiltonian, plus a distributed gaussian expansion scheme to the solution of the Liouville equation for the phase space distribution function. ...
Journal of Molecular Structure-Theochem, 2005
Web of Science® Times Cited
Physical Chemistry Chemical Physics, 2002
An approximate, computationally feasible expression for the rate constant is derived in terms of ... more An approximate, computationally feasible expression for the rate constant is derived in terms of a generalized formulation of the reaction path Hamiltonian, plus a distributed gaussian expansion scheme to the solution of the Liouville equation for the phase space distribution function. ...
The Journal of Chemical Physics, 2004
The coherent-state wave packet dynamics of several model systems is analyzed in terms of Bohm&... more The coherent-state wave packet dynamics of several model systems is analyzed in terms of Bohm's total potential. The quantum dynamics has been obtained by solving the time-dependent Schrodinger equation, and a method for obtaining the total potential from it, involving just matrix algebra, has been proposed. Contrary to what one may expect, it is shown that the time- and state-dependent features of the total potential admit a rationale, classical-like description of quantum effects, leading to a unified picture of them, which is not critically dependent, as for the key features, on the classical potential. An outstanding feature is found to be the relation of the state system's density amplitude and sharpness (in its dependence with position) with quantum effects. Sharp density profiles and low densities cause the total potential to strongly depart from the classical value, in both time regimes and position ranges, which provide a clearer, more deterministic view to quantum dynamics. Free motion as well as scattering processes by square and Eckart barriers have been analyzed by means of careful inspection of several time dependent snapshots. The result is an insightful picture of processes involving tunneling and antitunneling, including their dynamical variants, as well as resonances and quantization.
The Journal of Chemical Physics, 2002
A reaction path Hamiltonian is formulated in terms of a Newton reference path. The defining diffe... more A reaction path Hamiltonian is formulated in terms of a Newton reference path. The defining differential equation for the latter is solved by quadratically expanding the original equation, which in turn leads to an improved formulation of the reaction path Hamiltonian. This new reference ...
A Density Functional View, 2009
Chemical Physics Letters, 1991
... 3. Results of an extended 280 00092614 91 03.50 1991 Elsevier Science Publishers BV (NorthHol... more ... 3. Results of an extended 280 00092614 91 03.50 1991 Elsevier Science Publishers BV (NorthHolland) Parallel calculations of approximate 3D quantum cross sections: the Li + HF reaction Antonio Lagana, Xavier Gimenez Ernesto Garcia 2 ... Walkerand EF Hayes, J. Phys.Chem ...
Journal of Molecular Structure: THEOCHEM, 1988
ABSTRACT The ground state potential energy surface for the reaction on the title has been calcula... more ABSTRACT The ground state potential energy surface for the reaction on the title has been calculated at the UHF-MP3 level and built up by means of a spline procedure. The quantum reactive probabilities for the reaction obtained from hyperspherical calculations show a strong oscillatory behaviour and a number of sharp resonances.
Lecture Notes in Computer Science, 2005
Journal of Molecular Structure-theochem - J MOL STRUC-THEOCHEM, 1999
Extensive theoretical quantum-mechanical calculations are reported for the cross-section and rela... more Extensive theoretical quantum-mechanical calculations are reported for the cross-section and related dynamical quantities of the B+OH→BO+H reaction, on a previously developed potential-energy surface (PES) describing the ground electronic state. These calculations show, as an outstanding feature, the presence of marked structures in the shape of the excitation function as a consequence of the existence of a dense spectrum of rather long-lived resonance states. These are narrow enough to survive the angular momentum averaging, thanks to an important stabilization caused by an electronic minimum corresponding to a linear HOB configuration. The centrifugal barriers due to high values of the orbital angular momentum are found to lead to several orbiting shape resonances, as revealed by the opacity function plots and the dependence of the reaction probability on energy. Differential cross-sections corresponding to energies lying at either reactivity peaks or valleys in the integral cross...
The Journal of Physical Chemistry A, 1997
ABSTRACT In this Letter are presented three-dimensional quantum mechanical cross sections for the... more ABSTRACT In this Letter are presented three-dimensional quantum mechanical cross sections for the title reaction, as calculated for the ab initio potential energy surface of Urban, Jaquet, and Staemmler. The calculations were done within the coupled-states approximation. It is shown that not only are the J = 0 probabilities affected by numerous sharp resonances but even the energy-dependent cross sections, for which such resonances are expected to be smoothed out, are characterized by a rich resonance structure. This is the first time that such oscillatory integral cross sections have been obtained for a chemical exchange process. From comparison with quasi-classical-trajectory results, it is shown that the reaction is dominated by quantum effects to the extent that the quasi-classical-trajectory calculations sometimes become irrelevant.
… Theoretica Chimica Acta …, 1991
Summary Reactive Infinite Order Sudden Approximation calculations have been performed using a com... more Summary Reactive Infinite Order Sudden Approximation calculations have been performed using a computational procedure restructured to run on parallel computers. Computationally intensive sections of the code are analyzed and speedups obtained from a parallel ...
The Journal of Physical …, 1993
Extended approximate three-dimensional quantum calculations of the cross section and product vibr... more Extended approximate three-dimensional quantum calculations of the cross section and product vibrational distributions of the H+ F2-HF+ F reaction have been performed in order to carry out a comparison with existing information. It has been found that our calculations ...
Chemical Physics Letters, 1995
Docentes universitarios: una formación centrada en la práctica, 2020
En este capítulo mostramos evidencias de la reducida eficacia de la metodología tradicionalmente ... more En este capítulo mostramos evidencias de la reducida eficacia de la metodología tradicionalmente empleada en la educación universitaria (en comparación con lo que se logra mediante el aprendizaje activo) y proponemos que esta falta de eficacia puede solucionarse incorporando metodologías alter-nativas como el aprendizaje activo, el aprendizaje por medio de la indagación (“inquiry based learning”) y el aula invertida. Finalmente, mostraremos experiencias de los autores que demuestran la eficacia de la combinación del aula invertida con metodologías de aprendizaje activo y por medio de la indagación.