Juan ANTOLIN | University of Zaragoza (original) (raw)

Papers by Juan ANTOLIN

Zeitschrift f�r Physik D Atoms, Molecules and Clusters, 1996

ABSTRACT The Maximum-Entropy formalism is used to obtain approximations to the spherically averag... more ABSTRACT The Maximum-Entropy formalism is used to obtain approximations to the spherically averaged charge and momentum densities. The only information required is the first few radial expectation values. Analytical and numerical approximations to the central values of the densities are calculated. Moreover, the unused or unknown radial expectation values are estimated by means of the moments of these Maximum-Entropy densities. As illustration, the accuracy of these approximations are numerically studied in a Hartree-Fock framework. This method is complementary to the one which makes use of the Stieltjes-Chebyshev inequalities and leads to the least biased approximate densities compatible with the information we use.

Physica A: Statistical Mechanics and its Applications, 2013

Zeitschrift f�r Physik D Atoms, Molecules and Clusters, 1997

Physical Review a, Aug 1, 1994

J Phys B at Mol Opt Phys, 1993

It is shown how knowledge of a few low-order radial momenhlm expectation values ( p * ) and the c... more It is shown how knowledge of a few low-order radial momenhlm expectation values ( p * ) and the central value y(0) of the electron momentam density in atomic systems allows us to bound from below and h v e lhe momen" density y ( p ) for any value of the linear momentum, as well as the cumulative density and the cumulative radial density of any atom. The bounds are obtained by using Chebyshev inequalities and moment-theoxtic methods. Knowledge of a greater number of expectaxion values results in an improvement in the accuracy of the above mentioned bounds. A numerical study of this accuracy is canied out in a HartreeFock framework. Weslgate W M, Simas A M and Smith V H Jr 1985 3 . Chem. Phys. 83 4054 Williams B G (ed) 1977 Compton Scattering: The I~e~tigation of Electron Momentum DistribwIwns (New York Yue W and Janmin L 1984 Phys. Scr. 30 414 RCU) A I, Simas A M and Smith V H Jr 1981 Ckem Phys, 63 175

Theor Chem Acc, 2009

Theoretic-information measures of the Shannon type are employed to describe the course of the sim... more Theoretic-information measures of the Shannon type are employed to describe the course of the simplest hydrogen abstraction and the identity S N 2 exchange chemical reactions. For these elementary chemical processes, the transition state is detected and the bond breaking/forming regions are revealed. A plausibility argument of the former is provided and verified numerically. It is shown that the information entropy profiles posses much more chemically meaningful structure than the profile of the total energy for these chemical reactions. Our results support the concept of a continuum of transient of Zewail and Polanyi for the transition state rather than a single state, which is also in agreement with reaction force analyses. This is performed by following the intrinsic reaction coordinate (IRC) path calculated at the MP2 level of theory from which Shannon entropies in position and momentum spaces at the QCISD(T)/6-311??G(3df,2p) level are determined. Several selected descriptors of the density are utilized to support the observations, such as the molecular electrostatic potential, the hardness, the dipole moment along with geometrical parameters.

Physics Letters a, 2008

Using the Hartree-Fock non-relativistic wave functions in the position and momentum spaces, the s... more Using the Hartree-Fock non-relativistic wave functions in the position and momentum spaces, the statistical measure of complexity C, due to López-Ruiz, Mancini, and Calbet for the neutral atoms as well as their monopositive and mononegative ions with atomic number Z = 1-54 are reported. In C, given by the product of exponential power Shannon entropy and the average density, the latter is then replaced by the Fisher measure to obtain the Fisher-Shannon plane. Our numerical results suggest that in overall the Fisher-Shannon plane reproduces the trends given by C, with significantly enhanced sensitivity in the position, momentum and the product spaces in all neutral atoms and ions considered.

Journal of Mathematical Chemistry, 2012

We investigate the complexity of the hydrogenic identity S N 2 exchange reaction by means of info... more We investigate the complexity of the hydrogenic identity S N 2 exchange reaction by means of information-theoretic functionals such as disequilibrium (D), exponential entropy (L), Fisher information (I), power entropy (J) and joint information-theoretic measures, i.e., the I-D, D-L and I-J planes and the Fisher-Shannon (FS) and López-Mancini-Calbet (LMC) shape complexities. The several information-theoretic measures of the one-particle density were computed in position (r) and momentum (p) spaces. The analysis revealed that the chemically significant regions of this reaction can be identified through most of the information-theoretic functionals or planes, not only the ones which are commonly revealed by the energy, such as the reactant/product (R/P) and the transition state (TS), but also those that are not present in the energy profile such as the bond cleavage energy region (BCER), the bond breaking/forming regions (B-B/F) and the charge transfer process (CT). The analysis of the complexities shows that the energy profile of the identity S N 2 exchange reaction bears no simple behavior with respect to the LMC and FS measures. Most of the chemical features of interest (BCER, B-B/F and CT) are only revealed when particular information-theoretic aspects of localizability (L or J), uniformity (D) and disorder (I) are considered.

Physics Letters a, 1999

ABSTRACT

Chemical Physics Letters, May 1, 2009

Generalized Renyi complexity measures are defined and numerically analyzed for atomic one-particl... more Generalized Renyi complexity measures are defined and numerically analyzed for atomic one-particle densities in both conjugated spaces. These complexities provide, as particular cases, the previously known statistical and Fisher–Shannon complexities. The generalized complexities provide information on the atomic shell structure and shell-filling patterns, allowing to appropriately weight different regions of the electronic cloud.

Int J Quantum Chem, 2010

ABSTRACT Several measures of divergence have been used in the past to quantify the dissimilarity ... more ABSTRACT Several measures of divergence have been used in the past to quantify the dissimilarity between two or more one-particle atomic densities. The advantages and difficulties of them to capture the differences among different atomic systems in the position and momentum spaces are studied. One of these measures, the Jensen-Shannon divergence, is generalized giving rise to a one-parameter divergence, the Jensen-Rényi divergence, here proposed for a deep study of atomic systems, improving the above previous results. The versatility and power of this divergence is applied to compare different neutral atoms, their composing subshells and each of those atomic densities computed within different models. The parameter of the Jensen-Rényi Divergence allows also to emphasize the study in relevant specific regions of both conjugated spaces.

Chemical Physics Letters, 2015

ABSTRACT Relativistic effects in neutral atoms are analyzed, on the basis of discrepancies betwee... more ABSTRACT Relativistic effects in neutral atoms are analyzed, on the basis of discrepancies between the Hartree–Fock and Dirac–Fock electron charge densities. In doing so, comparative density functionals are employed as quantifiers of dissimilarity among the above densities. A detailed analysis throughout the Periodic Table reveals the relevance not only of weightiness for the systems considered, but also of their shell structure.

The positivity hypothesis on an unknown function X*(x), related to the imaginary part of the K+-p... more The positivity hypothesis on an unknown function X*(x), related to the imaginary part of the K+-p scattering amplitude on the unphysical region, allows the construction of a Stieltjes function H(z), known in a discrete set of real points and affected by errors owing to experimental measurements. The Stieltjes character of H(z) imposes constraints on the coefficients of its formal expansion which limit the universe of approximant functions, so acting as stabilizers of the analytic extrapolation. The Pade approximants (P.A.) to H(z), built with the coefficients of the formal expansion, provide rigorous bounds on the function in the cut complex plane. These bounds on H(z) can be translated to the K+- amplitude, F±(ω), obtaining bounds on the coupling constants g KNΛ 2 and g KNΣ 2 . Taking advantage of the fact that P.A. are valid for complex values of z, the position of the complex conjugate zeros of the amplitude has also been calculated. The consistency of the calculated real part ha...

Information Theory (IT) concepts are at the borderline of the development of the physical science... more Information Theory (IT) concepts are at the borderline of the development of the physical sciences which are attracting the attention of numerous researchers. In the present review article we discuss several applications of IT to the study of chemical systems and processes. This area of inquiry is shedding new light on the conceptual foundations of quantum chemistry and physics and is also at the core of the new field of Quantum Information Theory, which foresees important technological developments through concepts such as "entanglement", "teleportation" and "quantum computation".

ABSTRACT Within the present work on the meaning, interpretation and applications of the complexit... more ABSTRACT Within the present work on the meaning, interpretation and applications of the complexity measures, different order-uncertainty planes embodying relevant information-theoretical magnitudes are studied in order to analyse the information content of the position and momentum electron densities of several atomic (neutrals, singly-charged ions, isoelectronic series) and molecular (closed shells, radicals, isomers) systems. The quantities substaining those planes are the exponential and the power Shannon entropies, the disequilibrium, the Fisher information and the variance. Each plane gives rise to a measure of complexity, determined by the product of its components. In the present work, the values of the so-called López-Ruiz, Mancini and Calbet (LMC), Fisher-Shannon (FS) and Cramér-Rao (CR) complexities will be provided in both conjugated spaces and interpreted from physical and chemical points of view. Computations for atoms were carried out within a Hartree-Fock framework, while for molecules by means of CISD(T)/6-311++G(3df, 2p) wave functions. In order to have a complete information-theoretical description of these systems, it appears relevant to consider simultaneously the results in both spaces.

Physical Review A, 2014

Relativistic effects in one-particle densities of hydrogenic systems are quantified by means of g... more Relativistic effects in one-particle densities of hydrogenic systems are quantified by means of global and local density functionals: the Jensen-Shannon and the Jensen-Fisher divergences, respectively. The Schrödinger and Dirac radial densities are compared, providing complementary results in position and momentum spaces. While the electron cloud gets compressed towards the origin in the Dirac case, the momentum density spreads out over its domain, and the raising of minima in position space does not occur in the momentum space. Regarding the dependence on the nuclear charge and the state quantum numbers for all divergences here considered, as well as their mutual interconnection, accurate powerlike laws y ≈ Cx a are found systematically. The parameters {C,a} defining the respective dependences are extremely sensitive to the closeness of the system to the ground and/or the circular state. Particularly interesting are the analyses of (i) the plane subtended by the Jensen-Shannon and Jensen-Fisher divergences, in a given space (position or momentum), and (ii) either of the above two divergences in the position-momentum plane. These kinds of results show the complementary role of global and local divergences and that of both conjugate spaces.

Journal of Physics G-Nuclear and Particle Physics, 1986

... forward elastic amplitude J Antolin and A Cruz Departamento de Fisica Teorica, Facultad de Ci... more ... forward elastic amplitude J Antolin and A Cruz Departamento de Fisica Teorica, Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza, Spain Received 31 May 1985, in final form 5 August 1985 ... 298 J Antolin and A Cruz real and imaginary parts of the amplitude. ...