Quantum-chemically computed integral characteristics of complex nanomaterials

Development of theoretical tools to analyze electronic structure of complex nanomaterials depending on features of spatial and chemical organizations of different phases is of interest from both practical and theoretical points of view. Therefore, in this work, an approach based on computations of the atomic charge distribution functions (CDF) in parallel to calculations of the distribution functions of the chemical shifts (SDF) of protons is developed to be applied to a set of complex oxide and carbon nanomaterials. Binary nanooxides (alumina/silica, titania/silica), 3d-metal-doped anatase, activated carbon, carbon nanotube, fullerene C60, graphene oxide, and N-doped Kagome graphene are considered here as representatives of different classes of nanomaterials. The analyses of the CDF and SDF as nonlocal characteristics of certain kinds of atoms in complex systems provide a deeper insight into electronic structure features depending on composition of the materials, guest phase-doped host phase at various amounts of dopants, structure of O- and OH-containing surface sites, amounts and organization of adsorbed water, formation of neutral and charged surface functionalities, bonding of solvated ions, etc. The CDF of metal and hydrogen atoms (electron-donors) are more sensitive to the mentioned factors than the CDF of O, N, and C atoms (electron acceptors) in various systems. As a whole, the use of the CDF and SDF in parallel expands the tool possibility in detailed analysis of the structural and interfacial effects in dried and wetted complex nanomaterials.

Download Full-text

Atomic charge distribution functions as a tool to analyze electronic structure of molecular and cluster systems

International Journal of Quantum Chemistry ◽

10.1002/qua.26665 ◽

2021 ◽

Author(s):

Vladimir M. Gun'ko

Keyword(s):

Electronic Structure ◽

Charge Distribution ◽

Atomic Charge ◽

Distribution Functions ◽

Cluster Systems

Download Full-text

Effects of silica cluster size and charge state on integral characteristics

Himia Fizika ta Tehnologia Poverhni ◽

10.15407/hftp12.02.081 ◽

2021 ◽

Vol 12 (2) ◽

pp. 81-89

Author(s):

V. M. Gun’ko ◽

Keyword(s):

Density Functional ◽

Chemical Shifts ◽

Bound Water ◽

Distribution Functions ◽

Solid Particles ◽

Basis Set ◽

Dft Methods ◽

Electron States ◽

Solvation Effects ◽

Integral Characteristics

The model sizes of solid particles as well as used quantum chemical methods can affect results of calculations with density functional theory (DFT) methods. The aim of this study was to analyze the effects of the silica cluster sizes, a number of bound water molecules, protonation and deprotonation of silanols, addition of Eigen cation alone or solvated, attachment of anions F- and Cl- alone or solvated, and whole solvation effects (with SMD) with the DFT calculations using a functional ωB97X-D with the cc-pVDZ basis set. The calculations of the distribution functions of atom charges (CDF), chemical shifts of the proton resonance (SDF), and integral density of electron states (IDES) show that small clusters with 8 or 22 (SiO4/2) units could give rather inappropriate results in contrast to larger clusters with 44 or 88 units. This is due to the fact that the small silica clusters do not have appropriate capability for delocalization of excess charges that leads to certain distortion of the electron states of the whole system. The IDES are more sensitive with respect to the cluster charging and less sensitive to the solvation effects than the CDF and SDF. As a whole, the use of several types of the distribution functions, such as integral characteristics with the CDF, SDF, and IDES, allows one to obtain a more detailed picture on the interfacial phenomena at silica surface for neutral and charged systems.

Download Full-text

Mechanochemically Synthetized PAN-Based Co-N-Doped Carbon Materials as Electrocatalyst for Oxygen Evolution Reaction

Nanomaterials ◽

10.3390/nano11020290 ◽

2021 ◽

Vol 11 (2) ◽

pp. 290

Author(s):

Paulette Gómez-López ◽

José Ángel Salatti-Dorado ◽

Daily Rodríguez-Padrón ◽

Manuel Cano ◽

Clemente G. Alvarado-Beltrán ◽

...

Keyword(s):

Oxygen Evolution ◽

Photoelectron Spectroscopy ◽

Carbon Nanomaterials ◽

Carbon Materials ◽

Catalytic Performance ◽

X Ray Diffraction ◽

New Class ◽

Electrocatalytic Performance ◽

Alkaline Environments ◽

Metal Doped

We report a new class of polyacrylonitrile (PAN)-based Co-N-doped carbon materials that can act as suitable catalyst for oxygen evolution reactions (OER). Different Co loadings were mechanochemically added into post-consumed PAN fibers. Subsequently, the samples were treated at 300 °C under air (PAN-A) or nitrogen (PAN-N) atmosphere to promote simultaneously the Co3O4 species and PAN cyclization. The resulting electrocatalysts were fully characterized and analyzed by X-ray diffraction (XRD) and photoelectron spectroscopy (XPS), transmission (TEM) and scanning electron (SEM) microscopies, as well as nitrogen porosimetry. The catalytic performance of the Co-N-doped carbon nanomaterials were tested for OER in alkaline environments. Cobalt-doped PAN-A samples showed worse OER electrocatalytic performance than their homologous PAN-N ones. The PAN-N/3% Co catalyst exhibited the lowest OER overpotential (460 mV) among all the Co-N-doped carbon nanocomposites, reaching 10 mA/cm2. This work provides in-depth insights on the electrocatalytic performance of metal-doped carbon nanomaterials for OER.

Download Full-text

Electronic structure modulation of NiS2 by transition metal doping for accelerating the hydrogen evolution reaction

Journal of Materials Chemistry A ◽

10.1039/c8ta11286j ◽

2019 ◽

Vol 7 (9) ◽

pp. 4971-4976 ◽

Cited By ~ 21

Author(s):

Tongtong Wang ◽

Xiaosong Guo ◽

Jingyan Zhang ◽

Wen Xiao ◽

Pinxian Xi ◽

...

Keyword(s):

Electronic Structure ◽

Catalytic Activity ◽

Transition Metal ◽

Hydrogen Evolution Reaction ◽

Systematic Study ◽

First Principles ◽

Transition Metal Doping ◽

First Principles Calculations ◽

Structure Modulation ◽

Metal Doped

We give a systematic study of the HER catalytic activity of transition metal doped NiS2 by first principles calculations and experiments.

Download Full-text

Electronic Structure and Optical Properties of Non-Metals (N, F, P, Cl, S)-Doped Cubic NaTaO3 by Density Functional Theory

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.79-82.1245 ◽

2009 ◽

Vol 79-82 ◽

pp. 1245-1248 ◽

Cited By ~ 12

Author(s):

Pei Lin Han ◽

Xiao Jing Wang ◽

Yan Hong Zhao ◽

Chang He Tang

Keyword(s):

Density Functional Theory ◽

Optical Properties ◽

Electronic Structure ◽

Visible Light ◽

Absorption Edge ◽

Density Functional ◽

Red Shift ◽

Functional Theory ◽

Photoactive Materials ◽

Metal Doped

Electronic structure and optical properties of non-metals (N, S, F, P, Cl) -doped cubic NaTaO3 were investigated systematically by density functional theory (DFT). The results showed that the substitution of (N, S, P, Cl) for O in NaTaO3 was effective in narrowing the band-gap relative to the F-doped NaTaO3. The larger red shift of the absorption edge and the higher visible light absorption at about 520 nm were found for the (N and P)-doped NaTaO3. The excitation from the impurity states to the conduction band may account for the red shift of the absorption edge in an electron-deficiency non-metal doped NaTaO3. The obvious absorption in the visible light region for (N and P)-doped NaTaO3 provides an important guidance for the design and preparation of the visible light photoactive materials.

Download Full-text

Inverted Cucurbit[n]urils: Density Functional Investigations on the Electronic Structure, Electrostatic Potential, and NMR Chemical Shifts

The Journal of Physical Chemistry A ◽

10.1021/jp809293s ◽

2009 ◽

Vol 113 (7) ◽

pp. 1368-1376 ◽

Cited By ~ 22

Author(s):

Rahul V. Pinjari ◽

Shridhar P. Gejji

Keyword(s):

Electronic Structure ◽

Electrostatic Potential ◽

Density Functional ◽

Chemical Shifts ◽

Nmr Chemical Shifts

Download Full-text

Evaluating electronic structure methods for accurate calculation of 19 F chemical shifts in fluorinated amino acids

Journal of Computational Chemistry ◽

10.1002/jcc.24919 ◽

2017 ◽

Vol 38 (30) ◽

pp. 2605-2617 ◽

Cited By ~ 8

Author(s):

Jayangika N. Dahanayake ◽

Chandana Kasireddy ◽

Jonathan M. Ellis ◽

Derek Hildebrandt ◽

Olivia A. Hull ◽

...

Keyword(s):

Amino Acids ◽

Electronic Structure ◽

Chemical Shifts ◽

Accurate Calculation ◽

Fluorinated Amino Acids ◽

Electronic Structure Methods

Download Full-text

Electron Energy Distribution Functions of Hydrogen: The Effect of Superelastic Vibrational Collisions and of the Dissociation Process

Zeitschrift für Naturforschung A ◽

10.1515/zna-1979-0511 ◽

1979 ◽

Vol 34 (5) ◽

pp. 585-593 ◽

Cited By ~ 15

Author(s):

M. Capitelli ◽

M. Dilonardo

Keyword(s):

Boltzmann Equation ◽

Energy Distribution ◽

Electron Energy ◽

Distribution Functions ◽

Electron Energy Distribution ◽

Hydrogen Atoms ◽

Dissociation Process ◽

Excitation Rate ◽

The Boltzmann Equation ◽

Energy Distribution Functions

Abstract Electron energy distribution functions (EDF) of molecular H2 have been calculated by numerically solving the Boltzmann equation including all the inelastic processes with the addition of superelastic vibrational collisions and of the hydrogen atoms coming from the dissociation process. The population densities of the vibrational levels have been obtained both by assuming a Boltz-mann population at a vibrational temperature different from the translational one and by solving a system of vibrational master equations coupled to the Boltzmann equation. The results, which have been compared with those corresponding to a vibrationally cold molecular gas, show that the inclusion of superelastic collisions and of the parent atoms affects the EDF tails without strongly modifying the EDF bulk. As a consequence the quantities affected by the EDF bulk, such as average and characteristic energies, drift velocity, 0-1 vibrational excitation rate are not too much affected by the inclusion of superelastic vibrational collisions and of parent atoms, while a strong influence is observed on the dissociation and ionization rate coefficients which depend on the EDF tail. Calculated dissociation rates, obtained by EDF's which take into account both the presence of vibrationally excited molecules and hydrogen atoms, are in satisfactory agreement with experimental results.

Download Full-text