Density Functional Theory Simulations of Nanostructures

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Theory and Simulation of Nanostructures".

Deadline for manuscript submissions: closed (15 March 2022) | Viewed by 7256

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Inorganic Chemistry at the Chemistry Department, University of Padova, 35131 Padova, Italy
Interests: surface-supported-supramolecular-architectures; transition metal complexes; DFT; X-ray absorption spectroscopy
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Dear Colleagues,

First principle quantum mechanical calculations are by now considered a sort of new spectroscopy, as it has been widely recognized that the chemical and structural information they provide is often more accessible and likewise reliable than that provided by conventional spectroscopies. Terms like in silico design or high-throughput computational approaches have become more and more familiar to the scientific community thanks to the development of computational modeling activities. Computational approaches are of paramount importance in the field of nanoscience to understand the physics of nanomaterials, to provide interpretative and predictive models of their structure/properties relationships as well as to design better nanomaterials-based devices. Among the powerful weapons in the computational chemist’s arsenal for attacking the structure/properties relationships of molecules, crystals, and nanostructured materials, the density functional theory (DFT) plays a unique role because it corresponds to an exact theory whose basic variable is the electron density rather than the wave function. The advantage is evident: different from the latter,  is an observable simply corresponding to the single-particle density revealed in the diffraction measurements. In the few last decades, the quantitative predictive role of DFT-based simulations has been increasingly exploited covering a range of applications including solid-state physics, materials science, chemistry, and biology. Today, we can say without fear of contradiction that DFT is an irreplaceable tool to rationalize experimental evidence as well as drive experiments towards the desired outcomes in a sort of reciprocal cross-fertilization. As such, the availability of increasingly powerful computing hardware, faster algorithms, and smarter workflows allow scientists to handle models consisting of about a thousand atoms, able to provide predictive information about the structure and properties of novel materials with new functionalities and improved in-service performance, thus allowing the design of more competitive products that can minimize the impact on the environment and the consumption of natural resources.

This Special Issue of Nanomaterials will cover the most recent advances in the DFT-based simulations of nanostructures of different dimensionalities with particular attention to the modeling of structural and functional properties of nanomaterials.

Prof. Dr. Maurizio Casarin
Guest Editor

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Keywords

  • materials science
  • nanomaterials
  • computational science
  • theoretical modeling
  • density functional theory

Published Papers (4 papers)

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Research

13 pages, 3028 KiB  
Article
Computational NEXAFS Characterization of Molecular Model Systems for 2D Boroxine Frameworks
by Daniele Toffoli, Elisa Bernes, Albano Cossaro, Gabriele Balducci, Mauro Stener, Silvia Mauri and Giovanna Fronzoni
Nanomaterials 2022, 12(9), 1610; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12091610 - 09 May 2022
Cited by 1 | Viewed by 1310
Abstract
The electronic properties of 2D boroxine networks are computationally investigated by simulating the NEXAFS spectra of a series of molecular models, with or without morphologic defects, with respect to the ideal honeycomb structure. The models represent portions of an irregular 2D boroxine framework [...] Read more.
The electronic properties of 2D boroxine networks are computationally investigated by simulating the NEXAFS spectra of a series of molecular models, with or without morphologic defects, with respect to the ideal honeycomb structure. The models represent portions of an irregular 2D boroxine framework obtained experimentally, as supported by the Au(111) surface. The B K-edge NEXAFS spectra are calculated within the transition potential (TP) approximation (DFT-TP). The role of the Au(111) supporting surface on the spectral features has also been investigated by comparing the calculated spectra of a defect-rich model in its free-standing and supported form. The calculated NEXAFS spectra differ from the experimental ones, as the position of the main resonance does not match in the two cases. This finding could suggest the presence of a strong interaction of the 2D boroxine network with the Au substrate, which is not captured in the model calculations. However, good agreement between measured and calculated B K-edge NEXAFS spectra is obtained for a model system, namely, trihydroxy boroxine, in which the B atoms are less screened by the valence electrons compared to the B–B linked boroxine network models considered here. These results suggest catalytic activity in the gold substrate in promoting a weakening or even the breaking of the B–B bond, which is not revealed by calculations. Full article
(This article belongs to the Special Issue Density Functional Theory Simulations of Nanostructures)
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12 pages, 3892 KiB  
Article
Spin-Orbit Coupling and Spin-Polarized Electronic Structures of Janus Vanadium-Dichalcogenide Monolayers: First-Principles Calculations
by Ming-Hao Lv, Chang-Ming Li and Wei-Feng Sun
Nanomaterials 2022, 12(3), 382; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12030382 - 24 Jan 2022
Cited by 10 | Viewed by 3070
Abstract
Phonon and spintronic structures of monolayered Janus vanadium-dichalcogenide compounds are calculated by the first-principles schemes of pseudopotential plane-wave based on spin-density functional theory, to study dynamic structural stability and electronic spin-splitting due to spin-orbit coupling (SOC) and spin polarization. Geometry optimizations and phonon-dispersion [...] Read more.
Phonon and spintronic structures of monolayered Janus vanadium-dichalcogenide compounds are calculated by the first-principles schemes of pseudopotential plane-wave based on spin-density functional theory, to study dynamic structural stability and electronic spin-splitting due to spin-orbit coupling (SOC) and spin polarization. Geometry optimizations and phonon-dispersion spectra demonstrate that vanadium-dichalcogenide monolayers possess a high enough cohesive energy, while VSTe and VTe2 monolayers specially possess a relatively higher in-plane elastic coefficient and represent a dynamically stable structure without any virtual frequency of atomic vibration modes. Atomic population charges and electron density differences demonstrate that V–Te covalent bonds cause a high electrostatic potential gradient perpendicular to layer-plane internal VSTe and VSeTe monolayers. The spin polarization of vanadium 3d-orbital component causes a pronounced energetic spin-splitting of electronic-states near the Fermi level, leading to a semimetal band-structure and increasing optoelectronic band-gap. Rashba spin-splitting around G point in Brillouin zone can be specifically introduced into Janus VSeTe monolayer by strong chalcogen SOC together with a high intrinsic electric field (potential gradient) perpendicular to layer-plane. The vertical splitting of band-edge at K point can be enhanced by a stronger SOC of the chalcogen elements with larger atom numbers for constituting Janus V-dichalcogenide monolayers. The collinear spin-polarization causes the band-edge spin-splitting across Fermi level and leads to a ferrimagnetic order in layer-plane between V and chalcogen cations with higher α and β spin densities, respectively, which accounts for a large net spin as manifested more apparently in VSeTe monolayer. In a conclusion for Janus vanadium-dichalcogenide monolayers, the significant Rashba splitting with an enhanced K-point vertical splitting can be effectively introduced by a strong SOC in VSeTe monolayer, which simultaneously represents the largest net spin of 1.64 (ћ/2) per unit cell. The present study provides a normative scheme for first-principles electronic structure calculations of spintronic low-dimensional materials, and suggests a prospective extension of two-dimensional compound materials applied to spintronics. Full article
(This article belongs to the Special Issue Density Functional Theory Simulations of Nanostructures)
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16 pages, 3093 KiB  
Article
The Magnetic Behaviour of CoTPP Supported on Coinage Metal Surfaces in the Presence of Small Molecules: A Molecular Cluster Study of the Surface trans-Effect
by Silvia Carlotto, Iulia Cojocariu, Vitaliy Feyer, Luca Floreano and Maurizio Casarin
Nanomaterials 2022, 12(2), 218; https://0-doi-org.brum.beds.ac.uk/10.3390/nano12020218 - 10 Jan 2022
Cited by 4 | Viewed by 1592
Abstract
Density functional theory, combined with the molecular cluster model, has been used to investigate the surface trans-effect induced by the coordination of small molecules L (L = CO, NH3, NO, NO2 and O2) on the cobalt electronic [...] Read more.
Density functional theory, combined with the molecular cluster model, has been used to investigate the surface trans-effect induced by the coordination of small molecules L (L = CO, NH3, NO, NO2 and O2) on the cobalt electronic structure of cobalt tetraphenylporphyrinato (CoTPP) surface-supported on coinage metal surfaces (Cu, Ag, and Au). Regardless of whether L has a closed- or an open-shell electronic structure, its coordination to Co takes out the direct interaction between Co and the substrate eventually present. The CO and NH3 bonding to CoTPP does not influence the Co local electronic structure, while the NO (NO2 and O2) coordination induces a Co reduction (oxidation), generating a 3d8 CoI (3d6 CoIII) magnetically silent closed-shell species. Theoretical outcomes herein reported demonstrate that simple and computationally inexpensive models can be used not only to rationalize but also to predict the effects of the Co–L bonding on the magnetic behaviour of CoTPP chemisorbed on coinage metals. The same model may be straightforwardly extended to other transition metals or coordinated molecules. Full article
(This article belongs to the Special Issue Density Functional Theory Simulations of Nanostructures)
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10 pages, 5607 KiB  
Article
Ultrahigh Spin Filter Efficiency, Giant Magnetoresistance and Large Spin Seebeck Coefficient in Monolayer and Bilayer Co-/Fe-/Cu-Phthalocyanine Molecular Devices
by Jianhua Liu, Kun Luo, Hudong Chang, Bing Sun and Zhenhua Wu
Nanomaterials 2021, 11(10), 2713; https://0-doi-org.brum.beds.ac.uk/10.3390/nano11102713 - 14 Oct 2021
Cited by 5 | Viewed by 1663
Abstract
The spin related electrical and thermoelectric properties of monolayer and bilayer MPc (M = Co, Fe, Cu) molecular devices in a parallel spin configuration (PC) and an anti-parallel spin configuration (APC) between the V-shaped zigzag-edged graphene nanoribbon electrodes and the center bilayer MPc [...] Read more.
The spin related electrical and thermoelectric properties of monolayer and bilayer MPc (M = Co, Fe, Cu) molecular devices in a parallel spin configuration (PC) and an anti-parallel spin configuration (APC) between the V-shaped zigzag-edged graphene nanoribbon electrodes and the center bilayer MPc molecules are investigated by combining the density functional theory and non-equilibrium Green’s function approaches. The results show that there is an ultrahigh spin filter efficiency exceeding 99.99995% and an ultra-large total conductance of 0.49996G0 for FePc-CoPc molecular devices in the PC and a nearly pure charge current at high temperature in the APC and a giant MR ratio exceeding 9.87 × 106% at a zero bias. In addition, there are pure spin currents for CuPc and FePc molecular devices in the PC, and an almost pure spin current for FePc molecular devices in the APC at some temperature. Meanwhile, there is a high SFE of about 99.99585% in the PC and a reserved SFE of about −19.533% in the APC and a maximum MR ratio of about 3.69 × 108% for the FePc molecular device. Our results predict that the monolayer and bilayer MPc (M = Co, Fe, Cu) molecular devices possess large advantages in designing high-performance electrical and spintronic molecular devices. Full article
(This article belongs to the Special Issue Density Functional Theory Simulations of Nanostructures)
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