Search Results - "Ciencias físicas"

1

article

A decomposition of the number of effectively unpaired electrons and its physical meaning

Authors: Lain, Luis; Torre, Alicia; Alcoba, Diego Ricardo; Bochicchio, Roberto Carlos

Publication Date: 2009.

Language: English.

Abstract:

We report a procedure which allows one to decompose the number of effectively unpaired electrons corresponding to an N-electron system into two components with well-defined physical meaning. One of these terms represents the number of net unpaired electrons arising from the spin. The second one accounts for the partial split of electron pairs that appears when multideterminantal correlated wave functions are used. © 2009 Elsevier B.V. All rights reserved.

Author affiliation: Lain, Luis. Universidad del Pais Vasco - Euskal Herriko Unibertsitatea, Campus Bizkaia; España

Author affiliation: Torre, Alicia. Universidad del Pais Vasco - Euskal Herriko Unibertsitatea, Campus Bizkaia; España

Author affiliation: Alcoba, Diego Ricardo. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina

Author affiliation: Bochicchio, Roberto Carlos. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina

Keywords: EFFECTIVELY UNPAIRED DENSITY MATRIX; CUMULANTS; SPIN DENSITY; ELECTRON PAIRS; Astronomía; Ciencias Físicas; CIENCIAS NATURALES Y EXACTAS.

Repository: CONICET Digital (CONICET). Consejo Nacional de Investigaciones Científicas y Técnicas

2

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A study of the relationships between unpaired electron density, spin-density and cumulant matrices

Authors: Lain, Luis; Torres, Alicia Ines; Alcoba, Diego Ricardo; Bochicchio, Roberto Carlos

Publication Date: 2011.

Language: English.

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Abstract:

This work describes the derivation of simple relationships between the density matrix of effectively unpaired electrons and the spin-density matrix in N-electron systems. The link between both devices turns out to be the one-electron matrix arising from the diagonal contraction of the cumulant matrix corresponding to the second-order reduced density matrix. We study some features of this contracted matrix, showing its usefulness to describe the electronic correlation. Numerical determinations performed in selected systems with different spin symmetries confirm the theoretical predictions. © 2010 Springer-Verlag.

Author affiliation: Lain, Luis. Universidad del Pais Vasco - Euskal Herriko Unibertsitatea, Campus Bizkaia;

Author affiliation: Torres, Alicia Ines. Universidad del Pais Vasco - Euskal Herriko Unibertsitatea, Campus Bizkaia;

Author affiliation: Alcoba, Diego Ricardo. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina

Author affiliation: Bochicchio, Roberto Carlos. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina

Keywords: CUMULANT MATRICES; ELECTRON CORRELATION; REDUCED DENSITY MATRICES; Astronomía; Ciencias Físicas; CIENCIAS NATURALES Y EXACTAS.

Repository: CONICET Digital (CONICET). Consejo Nacional de Investigaciones Científicas y Técnicas

3

article

An orbital localization criterion based on the theory of "fuzzy" atoms

Authors: Alcoba, Diego Ricardo; Lain, Luis; Torre, Alicia; Bochicchio, Roberto Carlos

Publication Date: 2006.

Language: English.

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Abstract:

This work proposes a new procedure for localizing molecular and natural orbitals. The localization criterion presented here is based on the partitioning of the overlap matrix into atomic contributions within the theory of "fuzzy" atoms. Our approach has several advantages over other schemes: it is computationally inexpensive, preserves the σ/π-separability in planar systems and provides a straightforward interpretation of the resulting orbitals in terms of their localization indices and atomic occupancies. The corresponding algorithm has been implemented and its efficiency tested on selected molecular systems. © 2006 Wiley Periodicals, Inc.

Author affiliation: Alcoba, Diego Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina

Author affiliation: Lain, Luis. Universidad del Pais Vasco - Euskal Herriko Unibertsitatea, Campus Bizkaia; España

Author affiliation: Torre, Alicia. Universidad del Pais Vasco - Euskal Herriko Unibertsitatea, Campus Bizkaia; España

Author affiliation: Bochicchio, Roberto Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina

Keywords: "FUZZY" ATOMS; ORBITAL LOCALIZATION CRITERION; Astronomía; Ciencias Físicas; CIENCIAS NATURALES Y EXACTAS.

Repository: CONICET Digital (CONICET). Consejo Nacional de Investigaciones Científicas y Técnicas

4

article

Covalent bond indices and ionicities from similarity measures

Authors: Alcoba, Diego Ricardo; Bochicchio, Roberto Carlos; Lain, Luis; Torre, Alicia

Publication Date: 2007.

Language: English.

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Repository: CONICET Digital (CONICET). Consejo Nacional de Investigaciones Científicas y Técnicas

5

article

Covalent bond orders revisited: The open-shell case

Authors: Alcoba, Diego Ricardo; Bochicchio, Roberto Carlos; Blainq, Luis; Torres, Alicia Ines

Publication Date: 2008.

Language: English.

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Abstract:

This article states the concept of covalent bond order for open-shell systems from the invariance properties of the first- and second-order reduced density matrices for all the components of a multiplet state. A general bond order definition is formulated in the framework of the electronic population analyses in the Hilbert space of atomic orbitals. © the Owner Societies.

Author affiliation: Alcoba, Diego Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina

Author affiliation: Bochicchio, Roberto Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina

Author affiliation: Blainq, Luis. Departamento de Química, Física, Facultad de Ciencias, Universidad del País Vasco, España; Argentina

Author affiliation: Torres, Alicia Ines. Departamento de Química, Física, Facultad de Ciencias, Universidad del País Vasco, ; España

Keywords: REDUCED DENSITY MATERICES; COVALENT BOND ORDERS; SPIN DENSITY; Astronomía; Ciencias Físicas; CIENCIAS NATURALES Y EXACTAS.

Repository: CONICET Digital (CONICET). Consejo Nacional de Investigaciones Científicas y Técnicas

6

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Decomposition of the first-order reduced density matrix: An isopycnic localization treatment

Authors: Alcoba, Diego Ricardo; Bochicchio, Roberto Carlos; Torre, Alicia; Lain, Luis

Publication Date: 2006.

Language: English.

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Abstract:

In this work, we propose a partitioning of the first-order reduced density matrix corresponding to an N-electron system into first-order reduced density matrices associated with regions defined in the real space (regional matrices). The treatment is based on an isopycnic orbital localization transformation that provides regional matrices that are diagonalized by identical localized orbitals, having many attributes associated with chemical concepts (appropriate localization in space, high transferability, etc.). Although the obtained numerical values are similar to those arising from previous studies, their interpretation is more rigorous and the computational cost is much lower. © 2006 American Chemical Society.

Author affiliation: Alcoba, Diego Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina

Author affiliation: Bochicchio, Roberto Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina

Author affiliation: Torre, Alicia. Universidad del País Vasco; España

Author affiliation: Lain, Luis. Universidad del País Vasco; España

Keywords: Astronomía; Ciencias Físicas; CIENCIAS NATURALES Y EXACTAS.

Repository: CONICET Digital (CONICET). Consejo Nacional de Investigaciones Científicas y Técnicas

7

article

Depicting electronic distributions from accurate computational first principles: On the relationship between the complex patterns of bonding interaction and the back-donation pheno...

Authors: Lobayan, Rosana Maria; Bochicchio, Roberto Carlos; Pérez del Valle, Carlos

Publication Date: 2016.

Language: English.

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Abstract:

A detailed theoretical description of metal?ligand interactions in the case of the simple isoelectronic transition metal series Ni, Cu+, Zn2 and one C2H4 ligand is presented. This task is performed in terms of the local and nonlocal topology-based formalisms of the electronic density and its decomposition into paired and unpaired contributions. The analysis is mainly focused on the nature of the carbon?metal interactions under the traditional chemical back-donation phenomena and the relationship with the existence of two-electron three-center (2e-3c) complex patterns of bonding, that is, 2e-3c atomic interactions. For these simple prototypical systems, which seem to be adequate examples to describe the topologic features of such electron distribution in terms of the density point of view, both phenomena, that is, the back-donation and the 2e-3c interactions, are mutually exclusive.

Author affiliation: Lobayan, Rosana Maria. Universidad Nacional del Nordeste; Argentina

Author affiliation: Bochicchio, Roberto Carlos. Universidad de Buenos Aires. Facultad de Ciencias Exactas. Departamento de Ecología, Genética y Evolución. Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina

Author affiliation: Pérez del Valle, Carlos. Universite Grenoble Alpes; Francia

Keywords: BACK-DONATION; COMPLEX PATTERNS OF BONDING; ELECTRONIC DENSITY; ELECTRONIC DISTRIBUTION; TOPOLOGY; Astronomía; Ciencias Físicas; CIENCIAS NATURALES Y EXACTAS.

Repository: CONICET Digital (CONICET). Consejo Nacional de Investigaciones Científicas y Técnicas

8

article

Description of functional groups by means of domain-restricted reduced density matrices

Authors: Alcoba, Diego Ricardo; Torre, Alicia; Bochicchio, Roberto Carlos; Lain, Luis

Publication Date: 2007.

Language: English.

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Abstract:

This report constitutes an application of our previous theoretical works on partitionings of the first-order reduced density matrix according to the atomic domains defined in the theory of atoms in molecules. The numerical determinations obtained reveal that the domain-restricted reduced density matrices, which are the tools resulting from the former treatments, are suitable devices to describe chemical features of molecular fragments. We have focused attention on a study of functional groups in several series of organic compounds confirming the usefulness of these tools. © 2007 Springer-Verlag.

Author affiliation: Alcoba, Diego Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina

Author affiliation: Torre, Alicia. Universidad del País Vasco; España

Author affiliation: Bochicchio, Roberto Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina

Author affiliation: Lain, Luis. Universidad del País Vasco; España

Keywords: ATOMS IN MOLECULES; ELECTRON POPULATION; REDUCED DENSITY MATRICES; Astronomía; Ciencias Físicas; CIENCIAS NATURALES Y EXACTAS.

Repository: CONICET Digital (CONICET). Consejo Nacional de Investigaciones Científicas y Técnicas

9

article

Descriptions of local spins in the three-dimensional physical space

Authors: Alcoba, Diego Ricardo; Torre, Alicia; Lain, Luis; Bochicchio, Roberto Carlos

Publication Date: 2011.

Language: English.

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Abstract:

This report describes the partitioning of the expectation value of the spin-squared operator corresponding to an N-electron system in the three-dimensional physical space, according to the Bader and fuzzy atom approaches. Numerical determinations performed in selected open-shell systems at Hartree-Fock and density functional theory levels confirm the reliability of the local spins obtained. A comparison between these results and their counterpart ones arising from the partitioning in the Hilbert space is analyzed in detail. © 2011 Elsevier B.V. All rights reserved.

Author affiliation: Alcoba, Diego Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina

Author affiliation: Torre, Alicia. Universidad del País Vasco; España

Author affiliation: Lain, Luis. Universidad del País Vasco; España

Author affiliation: Bochicchio, Roberto Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina

Keywords: Astronomía; Ciencias Físicas; CIENCIAS NATURALES Y EXACTAS.

Repository: CONICET Digital (CONICET). Consejo Nacional de Investigaciones Científicas y Técnicas

10

article

Determination of energies and electronic densities of functional groups according to partitionings in the physical space

Authors: Alcoba, Diego Ricardo; Oña, Ofelia Beatriz; Torre, Alicia; Lain, Luis; Bochicchio, Roberto Carlos

Publication Date: 2008.

Language: English.

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Abstract:

This work formulates our previously reported partitionings of the first-order reduced density matrix and the molecular electronic energy using for both quantities an identical mathematical framework. The procedure provides a consistent and rigorous scheme for extending our algorithms to unions of atomic domains, in order to describe molecular fragments which can be identified as functional groups. Numerical determinations, performed in several series of organic compounds and clusters, support the reliability of our methodology to describe properties of atomic groups. © 2008 American Chemical Society.

Author affiliation: Alcoba, Diego Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina

Author affiliation: Oña, Ofelia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina

Author affiliation: Torre, Alicia. Universidad del País Vasco; España

Author affiliation: Lain, Luis. Universidad del País Vasco; España

Author affiliation: Bochicchio, Roberto Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina

Keywords: REDUCED DENSITY MATERICES; ATOMS IN MOLECULES; FUNCTIONAL GROUPS; PARTITIONINGS; Astronomía; Ciencias Físicas; CIENCIAS NATURALES Y EXACTAS.

Repository: CONICET Digital (CONICET). Consejo Nacional de Investigaciones Científicas y Técnicas

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