La simulación computacional en Química y Física

El artículo da a conocer la importancia de la simulación o modelado computacional en lo que se conoce como laboratorio virtual (en analogía a un laboratorio real), desde dos puntos de vista: la química cuántica computacional (QCC) y la física del estado sólido computacional (FESC), además de su aplicación y el perfil que deberá poseer el estudiante en estas áreas de la investigación. La aplicación de simulación es una prueba con la que el matemático John Pople y el físico Walter Kohn obtienen el premio Nobel de química en 1998. Ambos, fueron creadores del programa molecular "Gaussian", que implementa las dos principales teorías para el estudio de sistemas moleculares (teoría Hartree-Fock (HF) y teoría de las funcionales de la densidad (DFT)

Chemical and Physical Viewpoints About the Bonding in Fullerene- Graphene Hybrid Materials: Interaction on Pristine and Fe-Doped Graphene

A DFT scheme was adopted to study the noncovalent/covalent attachment of fullerenes (C-60, Si24C36, and B24N36) to graphene and Fe-doped graphene nanosheets (FeG). Geometrical, energetic, and electronic properties related to the physical and chemical nature of the bonding were characterized. The results show that fullerenes are physisorbed on graphene with adsorption energies of 0.7-1.2 eV, while the chemisorption is reached on FeG by cycloadditions with adsorption energies of 1.6-4.4 eV and is depending on the topology of FeG. The origin of the stability was analyzed from chemical and physical viewpoints, applying methods such as atom-in-molecules (AIM), natural bond orbital (NBO), and energy decomposition analysis based on absolutely localized molecular orbitals (ALMO-EDA). It is shown that noncovalent graphene-fullerene hybrids are assembled by van der Waals interactions but are also governed by permanent electrostatic Coulombic interactions that contribute at least 31% to the binding stability and depending on the bond polarity of fullerenes. Otherwise, the cycloaddition of fullerenes with FeG is reached by the formation of highly polarized chemical bonds, which were described in a detailed orbital picture. The structural stability of the covalent complexes is dominated by the contribution of charge transfer and permanent electrostatic physical effects. Additionally, the polarizability is an intrinsic property of fullerenes that also determines its binding strength on graphene (up to 35%); in this way, the larger polarizability of fullerenes increases the interaction stability. Therefore, this work gives insights into the bonding properties governing the stability of hybrid materials formed by self-assembly of fullerenes onto emerging low-dimensional nanostructures

Structural Stability and Electronic Properties of Boron Phosphide Nanotubes: A Density Functional Theory Perspective

Based on the Density Functional Theory (DFT) calculations, we analyze the structural and electronic properties of boron phosphide nanotubes (BPNTs) as functions of chirality. The DFT calculations are performed using the M06-2X method in conjunction with the 6-31G(d) divided valence basis set. All nanostructures, (n,0) BPNT (n = 5–8, 10, 12, 14) and (n,n) BPNT (n = 3–11), were optimized minimizing the total energy, assuming a non-magnetic nature and a total charge neutrality. Results show that the BPNT diameter size increases linearly with the chiral index “n” for both chiralities. According to the global molecular descriptors, the (3,3) BPNT is the most stable structure provided that it shows the largest global hardness value. The low chirality (5,0) BPNT has a strong electrophilic character, and it is the most conductive system due to the small |HOMO-LUMO| energy gap. The chemical potential and electrophilicity index in the zigzag-type BPNTs show remarkable chirality-dependent behavior. The increase in diameter/chirality causes a gradual decrease in the |HOMO-LUMO| energy gap for the zigzag BPNTs; however, in the armchair-type BPNTs, a phase transition is generated from a semiconductor to a conductor system. Therefore, the nanostructures investigated in this work may be suggested for both electrical and biophysical applications

Structural Stability and Electronic Properties of Boron Phosphide Nanotubes: A Density Functional Theory Perspective

Based on the Density Functional Theory (DFT) calculations, we analyze the structural and electronic properties of boron phosphide nanotubes (BPNTs) as functions of chirality. The DFT calculations are performed using the M06-2X method in conjunction with the 6-31G(d) divided valence basis set. All nanostructures, (n,0) BPNT (n = 5–8, 10, 12, 14) and (n,n) BPNT (n = 3–11), were optimized minimizing the total energy, assuming a non-magnetic nature and a total charge neutrality. Results show that the BPNT diameter size increases linearly with the chiral index “n” for both chiralities. According to the global molecular descriptors, the (3,3) BPNT is the most stable structure provided that it shows the largest global hardness value. The low chirality (5,0) BPNT has a strong electrophilic character, and it is the most conductive system due to the small |HOMO-LUMO| energy gap. The chemical potential and electrophilicity index in the zigzag-type BPNTs show remarkable chirality-dependent behavior. The increase in diameter/chirality causes a gradual decrease in the |HOMO-LUMO| energy gap for the zigzag BPNTs; however, in the armchair-type BPNTs, a phase transition is generated from a semiconductor to a conductor system. Therefore, the nanostructures investigated in this work may be suggested for both electrical and biophysical applications