STABILITIES AND FRAGMENTATION BEHAVIORS OF Agn CLUSTERS (n = 2–34)

2012 ◽  
Vol 11 (05) ◽  
pp. 953-964 ◽  
Author(s):  
WEI ZHANG ◽  
SHU-YAO YAN ◽  
ZENG-XIA ZHAO ◽  
HONG-XING ZHANG
Keyword(s):  
Molecular Orbital ◽  
Tight Binding ◽  
Silver Cluster ◽  
Dft Method ◽  
Binding Energies ◽  
Silver Clusters ◽  
Fragmentation Channel ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital ◽  
Homo Lumo

A global search on the lowest-energy structures of the medium-sized silver clusters Ag n(n = 21–34) was performed by using a genetic algorithm (GA) coupled with a tight-binding (TB) method. Structures, binding energies per atom, second differences in energies, the energy gaps between the highest occupied molecular orbital and the lowest unoccupied molecular orbital (HOMO–LUMO), and fragmentation behaviors of Ag n(n = 21–34) are investigated by using DFT method. The calculated results show that the neutral silver clusters prefer to decay by evaporation of a monomer except a small sized silver cluster ( Ag 4), which favors a dimmer evaporation. For the collision induced dissociation of cationic silver clusters, decaying a silver atom is found to be the dominant fragmentation channel. But for some small sized cationic silver clusters, a neutral dimmer evaporation is found to be energetically favorable. Our calculated results are consistent with previous studies.

Structural, stability, and vibrational properties of BinPm clusters

2018 ◽  
Vol 32 (10) ◽  
pp. 1850117
Author(s):  
Wanting Shen ◽  
Lihong Han ◽  
Dan Liang ◽  
Chunfang Zhang ◽  
Quhe Ruge ◽  
...  
Keyword(s):  
Optical Properties ◽  
Molecular Orbital ◽  
Binding Energies ◽  
Highest Occupied Molecular Orbital ◽  
Stable Clusters ◽  
Lowest Unoccupied Molecular Orbital ◽  
Energy Gains ◽  
Alloys And Compounds ◽  
Homo Lumo ◽  
Structure Calculations

An in-depth investigation is performed on stability mechanisms, electronic and optical properties of III–V semiconductor vapor phases clusters. First principles electronic structure calculations of CAM-B3LYP are performed on neutral Bi[Formula: see text]P[Formula: see text] (n + m [Formula: see text] 14) clusters. The geometrical evolution of all stable structures remains amorphous as the clusters size increases. Binding energies (BEs), energy gains and highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO–LUMO) gaps confirm that all four-atom structures of Bi[Formula: see text]P[Formula: see text] clusters have more stable optical properties. Orbitals composition and vibrational spectra of stable clusters are analyzed. Our calculations will contribute to the study of diluted bismuth alloys and compounds.

scholarly journals Geometry, Energy, and Some Electronic Properties of Carbon Polyprismanes: Ab Initio and Tight-Binding Study

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Konstantin P. Katin ◽  
Stanislav A. Shostachenko ◽  
Alina I. Avkhadieva ◽  
Mikhail M. Maslov
Keyword(s):  
Electronic Properties ◽  
Molecular Orbital ◽  
Density Functional ◽  
Tight Binding ◽  
Binding Energies ◽  
Effective Length ◽  
Binding Model ◽  
Highest Occupied Molecular Orbital ◽  
Semiconducting Properties ◽  
Lowest Unoccupied Molecular Orbital

We report geometry, energy, and some electronic properties of [n,4]- and [n,5]prismanes (polyprismanes): a special type of carbon nanotubes constructed from dehydrogenated cycloalkane C4- and C5-rings, respectively. Binding energies, interatomic bonds, and the energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) have been calculated using density functional approach and nonorthogonal tight-binding model for the systems up to thirty layers. It is found that polyprismanes become more thermodynamically stable as their effective length increases. Moreover, they may possess semiconducting properties in the bulk limit.

Investigation of Carbon Monoxide Adsorption on Cationic Gold- Palladium Clusters

2013 ◽  
Vol 68 (10-11) ◽  
pp. 651-658 ◽  
Author(s):  
Yang-Mei Chen ◽  
Xiao-Yu Kuang ◽  
Xiao-Wei Sheng ◽  
Huai-Qian Wang ◽  
Peng Shao ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Molecular Orbital ◽  
Density Functional ◽  
Co Adsorption ◽  
Vibration Strength ◽  
Au Clusters ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital ◽  
Pd Clusters ◽  
Homo Lumo

Density functional calculations have been performed for the carbon monoxide molecule adsorption on AunPd+m(n+m ≤ 6) clusters. In the process of CO adsorption, small Au clusters and Pd clusters tend to be an Au atom and three Pd atoms adsorption, respectively. For the mixed Au-Pd clusters, an Au atom, a Pd atom, two atoms consisted of an Au atom and a Pd atom, two Pd atoms, and three Pd atoms adsorption structures are displayed. The highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps and natural bond orbital charge population are calculated. Moreover, CO adsorption energy, CO stretching frequency, and CO bond length (upon adsorption) are also analysed in detail. The results predict that the adsorption strength of Au clusters with CO and the C-O vibration strength is enhanced and reduced after doping of Pd in the AunPdmCO+ complexes, respectively

Electronic and geometric structure of AuxCuy clusters studied by density functional theory

2014 ◽  
Vol 25 (06) ◽  
pp. 1450011 ◽  
Author(s):  
Y. Kadioglu ◽  
O. Üzengi Aktürk ◽  
M. Tomak
Keyword(s):  
Density Functional Theory ◽  
Molecular Orbital ◽  
Density Functional ◽  
Local Density ◽  
Three Dimensional ◽  
Binding Energies ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital

We have determined the stable structures of Au Cu n, Au 2 Cu n, Au 3 Cu n and Au x Cu 8-x clusters. It has been observed that Au Cu n, Au 2 Cu n and Au 3 Cu n systems have two-dimensional (2D) structures up to six atoms and they become three-dimensional (3D) afterwards. Au x Cu 8-x clusters favor 3D structures till the Au 7 Cu 1 cluster. We have found a lowest energy isomer of Au 6 Cu 2 from the literature. Bond lengths, binding energies, density of states (DOS), highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO-LUMO) gaps, ionization potential (IP) and electron affinity (EA) have been calculated for these structures using the first principles density functional theory (DFT) within the generalized gradient approximation (GGA) and the local density approximation (LDA). Generally, we have observed the overlap between s electrons of Cu and p electrons of Au near the Fermi level. Charge transfers are calculated by using the Löwdin analysis. It is observed that one Cu atom does not significantly modify the clusters which have more gold atoms. It is also seen that these clusters generally have nonmagnetic properties and results are consistent with the hybridization between s and d orbitals of Au in Au x Cu 8-x clusters.

QSAR Analyzes for the Predictive Toxicity of Substituted Phenols and Anilines to Fish (carp)

2013 ◽  
Vol 295-298 ◽  
pp. 109-112 ◽  
Author(s):  
Ping Sun ◽  
Shu Mei Gao ◽  
Hiu Liu ◽  
Jian Ting Chen
Keyword(s):  
Molecular Orbital ◽  
Dft Method ◽  
Qsar Model ◽  
Quantitative Structure Activity Relationship ◽  
Substituted Phenols ◽  
Substituted Anilines ◽  
Qsar Study ◽  
Highest Occupied Molecular Orbital ◽  
Main Effect ◽  
Lowest Unoccupied Molecular Orbital

A quantitative structure-activity relationship (QSAR) study for predicting the acute toxicity 96h - LC50 values of substituted anilines and phenols to carp is presented in this work. For this, the descriptors were obtained with DFT method at the B3LYP/6-311G** level using the Gaussian 03 software package. Afterwards the obtained parameters were taken as theoretical descriptors to establish a QSAR model for predicting -lgLC50. The model contains two variables, energy of the highest occupied molecular orbital (EHOMO) and energy of the lowest unoccupied molecular orbital (ELUMO), which suggest that the main effect on biological toxicity of phenols and anilines is the interaction of electrons between the molecules of organic chemicals. Besides, the model was further validated by variance inflation factors (VIF) and t-test, and show fine stabilities and predictive abilities, which can be used to predict -lgLC50 of these kinds of compounds.

Hückel Molecular Orbital Quantities of {X,Y}-Cyclacene Graphs Under Next-Nearest-Neighbour Approximations in Analytical Forms

2019 ◽  
Vol 74 (6) ◽  
pp. 469-488 ◽  
Author(s):  
Tapanendu Ghosh ◽  
Swapnadeep Mondal ◽  
Sukanya Mondal ◽  
Bholanath Mandal
Keyword(s):  
Molecular Orbital ◽  
Energy Difference ◽  
Triplet States ◽  
Nearest Neighbour ◽  
Geometrical Structures ◽  
Charge Densities ◽  
Absorption Energy ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital ◽  
Homo Lumo

AbstractHückel molecular orbital (HMO) quantities, viz., electron densities, charge densities, bond orders, free valences, total π-electron energies and highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO–LUMO) or band gaps of {X,Y}-cyclacene graphs under next-nearest-neighbour (nnn) approximations are expressed in analytical forms within a certain range of nnn approximation parameter (m). The critical values of m for {X,Y}-cyclacenes with varying X (=C, N, B) and Y (=C, N, B) are calculated. For {X,X}-cyclacenes with a π-electron on each atom, all HMO quantities except total π-electron energies for a given value of m are found to be independent of X. The cyclic dimer (CD) is constructed in obtaining the eigenvalues corresponding to the singular points of the density of states (DOS) of such {X,Y}-cyclacene. Although the HOMO–LUMO gap of the CD differs from that of the cyclacene with a large number of repeating units (i.e. n ⟶ ∞) but becomes the same for m = 0. The analytical expressions can be used for facile computer programming in obtaining the HMO quantities. Such nnn interaction approximations actually release, to some extent, the strain that results in due to the geometrical structures of such cyclacenes, which is evident from the plots of strain energy per segment vs. contribution of such interactions on the total π-electron energy, where the slopes decrease with an increase in m. The vertical absorption energy difference for singlet-triplet states bears excellent linear correlation with the HOMO–LUMO gaps for a certain m value (m = 0.3) in the case of an even n, but for an odd n, such energy difference remains invariant.

DFTB Calculation of Si Atomic Chains’ Structures and Electronic Properties

2016 ◽  
Vol 848 ◽  
pp. 494-497
Author(s):  
Xiu Min Xu ◽  
Li Jun Wu ◽  
Lin Zhang
Keyword(s):  
Electronic Properties ◽  
Molecular Orbital ◽  
Density Functional ◽  
Energy Gap ◽  
Tight Binding ◽  
Functional Theory ◽  
Symmetrical Distribution ◽  
Highest Occupied Molecular Orbital ◽  
Atomic Chains ◽  
Lowest Unoccupied Molecular Orbital

In this paper, structures and electronic properties of atomic chains with 5 to 20 silicon atoms and different atomic distances (d = 1.652 ~ 2.752Å) were calculated by the tight-binding method based on density functional theory. The results showed that the majority of the silicon atomic chains were symmetrical structures. When the number of silicon atoms was small, the silicon atomic chains were linear, when the silicon atomic chains had seven or more silicon atoms zigzag structures appeared. With the increase of the distance between atoms, atomic chains were gathering. When the number of silicon atoms was between 10 and 20, the charges on the silicon atoms appeared as a symmetrical distribution. With the increase of the number of atoms, the energy of silicon atomic chains decreased gradually. As the distance between atoms and atomic number changed, HOMO (highest occupied molecular orbital electrons) -LUMO (lowest unoccupied molecular orbital electrons) energy gap changed as well.

A New Class of Solar Cells: Isomeric Boron Carbide Semiconductors with Fourth Quadrant Conductivity

2003 ◽  
Vol 799 ◽  
Author(s):  
Ravi B. Billa ◽  
A. N. Caruso ◽  
J. I. Brand
Keyword(s):  
Boron Carbide ◽  
Molecular Orbital ◽  
Chemical Vapor ◽  
Fourth Quadrant ◽  
Neutron Detectors ◽  
New Class ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital ◽  
Aluminum Substrates ◽  
Homo Lumo

ABSTRACTPreviously, we have made diodes[1,2] and transistors [3] as well as very effective realtime solid state neutron detectors [4] out of semiconducting boron carbide deposited on silicon or silicon carbide‥In this work the recent fabrication of a new class of highly photosensitive boron carbide diodes is discussed. These diodes exploit the electronic behavior differences of the isomers of film precursors, the closo-dicarbododecaboranes. These differences were observed in photoemission and inverse photoemission studies where the HOMO-LUMO (highest occupied molecular orbital-lowest unoccupied molecular orbital) gap variations upon deposition varied strongly with the isomeric configuration. Based on these results, p-n junctions were formed by plasma enhanced chemical vapor of ortho and meta carborane, respectively, on both nickel and aluminum substrates. These diodes exhibit fourth-quadrant conductivity, making them exciting new photovoltaic conversion devices.

Antiaromatic ions and their value in quantifying aromaticity, as probes of delocalization, and potential as stable diradicals

2012 ◽  
Vol 84 (4) ◽  
pp. 1101-1112 ◽  
Author(s):  
Nancy S. Mills
Keyword(s):  
Chemical Shift ◽  
Molecular Orbital ◽  
Energetic Properties ◽  
Nucleus Independent Chemical Shift ◽  
Highest Occupied Molecular Orbital ◽  
Diradical Character ◽  
Aromatic Species ◽  
Lowest Unoccupied Molecular Orbital ◽  
Homo Lumo

Antiaromatic dications and dianions are available through oxidation or reduction of unsaturated precursors as well as through ionization of diols. Their experimental accessibility allows them to be used to evaluate the effectiveness of theoretical treatments of antiaromaticity such as the nucleus-independent chemical shift (NICS). Because measures of antiaromaticity are generally larger in magnitude than corresponding measures of aromaticity, they demonstrate relationships between different measures of aromaticity–antiaromaticity, such as those based on magnetic and energetic properties, more effectively than do aromatic measures. Antiaromatic species are more sensitive probes of delocalization than are aromatic species, giving the possibility of observation of subtle effects. Antiaromatic species possess a small highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO-LUMO) gap, giving rise to species with diradical character.

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