Ab InitioTheoretical Investigation on the Geometrical and Electronic Structures of Gallium Aurides:GaAun0/-andGa2Aun0/- (n=1–4)

This study presents a systematic investigation of the geometric and electronic properties of GaAun0/-and Ga2Aun0/-(n= 1–4) clusters based on density functional theory and wave function theory. Detailed orbital analyses, adaptive natural density partitioning, and electron localization function analyses are performed and relevant results are discussed. GaAun0/-(n= 1–4) clusters withn-Au terminals and Ga2Aun0/-(n= 1–4) clusters with bridged Au atoms possess geometric structures and bonding patterns similar to those of the corresponding gallium hydrides GaHn0/-and Ga2Hn0/-. Ga–Au interaction is predicted to occur through highly polar covalent bonds in monogallium aurides. In contrast to the highly symmetric ground states ofC2vGa2Au,C2vGa2Au2, andD3hGa2Au3,C3vGa2Au4is composed of strong interactions between a Ga+cation and the face of a tetrahedral GaAu4−anion. The adiabatic and vertical detachment energies of the anions under study are calculated to facilitate their experimental characterization. Geometric and electronic structural comparisons with the corresponding gallium hydrides are conducted to establish an isolobal analogy between gold and hydrogen atoms.

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Crystal structure of pomalidomide Form I, C13H11N3O4

Powder Diffraction ◽

10.1017/s0885715621000087 ◽

2021 ◽

pp. 1-6

Author(s):

James A. Kaduk ◽

Amy M. Gindhart ◽

Thomas N. Blanton

Keyword(s):

Crystal Structure ◽

Hydrogen Bonds ◽

Powder Diffraction ◽

Density Functional ◽

Double Layers ◽

Carbonyl Groups ◽

Hydrogen Atoms ◽

Powder Diffraction File ◽

Functional Theory ◽

Amine Hydrogen

The crystal structure of pomalidomide Form I has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Pomalidomide Form I crystallizes in the space group P-1 (#2) with a = 7.04742(9), b = 7.89103(27), c = 11.3106(6) Å, α = 73.2499(13), β = 80.9198(9), γ = 88.5969(6)°, V = 594.618(8) Å3, and Z = 2. The crystal structure is characterized by the parallel stacking of planes parallel to the bc-plane. Hydrogen bonds link the molecules into double layers also parallel to the bc-plane. Each of the amine hydrogen atoms acts as a donor to a carbonyl group in an N–H⋯O hydrogen bond, but only two of the four carbonyl groups act as acceptors in such hydrogen bonds. Other carbonyl groups participate in C–H⋯O hydrogen bonds. The powder pattern has been submitted to ICDD® for inclusion in the Powder Diffraction File™ (PDF®).

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Structural and computational investigation of an imine-based propeller-shaped macrocyclic cage

SN Applied Sciences ◽

10.1007/s42452-021-04255-7 ◽

2021 ◽

Vol 3 (2) ◽

Author(s):

Sriram Srinivasa Raghvan ◽

Suresh Madhu ◽

Velmurugan Devadasan ◽

Gunasekaran Krishnasamy

Keyword(s):

Band Gap ◽

Density Functional ◽

Strain Tensor ◽

Strong Interactions ◽

Soft Condensed Matter ◽

Functional Theory ◽

Self Assembling ◽

Phenyl Rings ◽

Crystal Volume

AbstractIn this study, we present the synthesis, spectroscopic and structural characterization of self-assembling gem-dimethyl imine based molecular cage (IMC). Self-assembling macrocycles and cages have well-defined cavities and have extensive functionalities ranging from energy storage, liquid crystals, and catalysts to water splitting photo absorber. IMC has large voids i.e., 25% of the total crystal volume thus could accommodate wide substrates. The synthesized imine-based molecular cages are stabilized by coaxial π bonded networks and long-range periodic van der Waal and non-bonded contacts as observed from the crystal structure. IMC also has typical properties of soft condensed matter materials, hence theoretical prediction of stress and strain tensor along with thermophysical properties were computed on crystal system and were found to be stable. Molecular dynamics revealed IMC is stabilized by, strong interactions between the interstitial phenyl rings. Density functional theory (DFT) based physicochemical properties were evaluated and has band gap of around 2.38ev (520 nm) similar to various photocatalytic band gap materials.

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Dumbbell configuration of silicon adatom defects on silicene nanoribbons

Scientific Reports ◽

10.1038/s41598-021-93465-5 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Huynh Anh Huy ◽

Quoc Duy Ho ◽

Truong Quoc Tuan ◽

Ong Kim Le ◽

Nguyen Le Hoai Phuong

Keyword(s):

Magnetic Properties ◽

Band Gap ◽

Density Functional ◽

Spin Moment ◽

Hydrogen Atoms ◽

Functional Theory ◽

Electronic And Magnetic Properties ◽

Spin Degeneracy ◽

Silicene Nanoribbons ◽

Formation Energies

AbstractUsing density functional theory (DFT), we performed theoretical investigation on structural, energetic, electronic, and magnetic properties of pure armchair silicene nanoribbons with edges terminated with hydrogen atoms (ASiNRs:H), and the absorptions of silicon (Si) atom(s) on the top of ASiNRs:H. The calculated results show that Si atoms prefer to adsorb on the top site of ASiNRs:H and form the single- and/or di-adatom defects depending on the numbers. Si absorption defect(s) change electronic and magnetic properties of ASiNRs:H. Depending on the adsorption site the band gap of ASiNRs:H can be larger or smaller. The largest band gap of 1 Si atom adsorption is 0.64 eV at site 3, the adsorption of 2 Si atoms has the largest band gap of 0.44 eV at site 1-D, while the adsorption at sites5 and 1-E turn into metallic. The formation energies of Si adsorption show that adatom defects in ASiNRs:H are more preferable than pure ASiNRs:H with silicon atom(s). 1 Si adsorption prefers to be added on the top site of a Si atom and form a single-adatom defect, while Si di-adatom defect has lower formation energy than the single-adatom and the most energetically favorable adsorption is at site 1-F. Si adsorption atoms break spin-degeneracy of ASiNRs:H lead to di-adatom defect at site 1-G has the highest spin moment. Our results suggest new ways to engineer the band gap and magnetic properties silicene materials.

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Theoretical Study on the Mechanism of Hydrogen Donation and Transfer for Hydrogen-Donor Solvents during Direct Coal Liquefaction

Catalysts ◽

10.3390/catal8120648 ◽

2018 ◽

Vol 8 (12) ◽

pp. 648 ◽

Cited By ~ 2

Author(s):

Haigang Hao ◽

Tong Chang ◽

Linxia Cui ◽

Ruiqing Sun ◽

Rui Gao

Keyword(s):

Density Functional ◽

Hydrogen Gas ◽

Hydrogen Donor ◽

Coal Liquefaction ◽

Hydrogen Atoms ◽

Functional Theory ◽

Donor Solvent ◽

National Energy Security ◽

Liquefaction Process ◽

Direct Coal Liquefaction

As a country that is poor in petroleum yet rich in coal, it is significant for China to develop direct coal liquefaction (DCL) technology to relieve the pressure from petroleum shortages to guarantee national energy security. To improve the efficiency of the direct coal liquefaction process, scientists and researchers have made great contributions to studying and developing highly efficient hydrogen donor (H-donor) solvents. Nevertheless, the details of hydrogen donation and the transfer pathways of H-donor solvents are still unclear. The present work examined hydrogen donation and transfer pathways using a model H-donor solvent, tetralin, by density functional theory (DFT) calculation. The reaction condition and state of the solvent (gas or liquid) were considered, and the specific elementary reaction routes for hydrogen donation and transfer were calculated. In the DCL process, the dominant hydrogen donation mechanism was the concerted mechanism. The sequence of tetralin donating hydrogen atoms was α-H (C1–H) > δ-H (C4–H) > β-H (C2–H) > γ-H (C3–H). Compared to methyl, it was relatively hard for benzyl to obtain the first hydrogen atom from tetralin, while it was relatively easy to obtain the second and third hydrogen atoms from tetralin. Comparatively, it was easier for coal radicals to capture hydrogen atoms from the H-donor solvent than to obtain hydrogen atoms from hydrogen gas.

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Density functional theory study of the role of benzylic hydrogen atoms in the antioxidant properties of lignans

Scientific Reports ◽

10.1038/s41598-018-30860-5 ◽

2018 ◽

Vol 8 (1) ◽

Cited By ~ 31

Author(s):

Quan V. Vo ◽

Pham Cam Nam ◽

Mai Van Bay ◽

Nguyen Minh Thong ◽

Nguyen Duc Cuong ◽

...

Keyword(s):

Density Functional Theory ◽

Density Functional ◽

Antioxidant Properties ◽

Density Functional Theory Study ◽

Hydrogen Atoms ◽

Functional Theory

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First-Principles Study of Interaction of Lithium Atoms with (3, 3) Carbon Nanotubes

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.687-691.4311 ◽

2014 ◽

Vol 687-691 ◽

pp. 4311-4314 ◽

Cited By ~ 1

Author(s):

Shun Fu Xu ◽

Ling Min Li

Keyword(s):

Carbon Nanotubes ◽

First Principles ◽

Density Functional ◽

Vacancy Defect ◽

Single Wall Carbon Nanotubes ◽

Generalized Gradient ◽

Hydrogen Atoms ◽

Functional Theory ◽

Vacancy Defects ◽

Adsorption Mechanisms

In this paper, we have employed first-principles calculations to investigate the adsorption mechanisms of one lithium atom on the sidewalls of 1/2/3 H-adsorbed indefective/defective (3, 3) single-wall carbon nanotubes (CNTs) which have vacancy defects. Our calculations are performed within density functional theory (DFT) under the generalized gradient approximation (GGA) of Perdew, Burke, and Ernzerhof (PBE).Our results show that the lithium atoms strongly binds to the H-adsorbed (3, 3) nanotube. Lithium atoms can chemically adsorb on (3, 3) nanotube with the vacancy defect (MVD) without any energy barrier. The lithium adsorption will enhance the electrical conductivity of the nanotube. Further more, the structure of the (3, 3) nanotube with the MVD and hydrogen atoms will become more stable after the three kinds of lithium adsorption.

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First-Principles Study of Ag3Sn, AgZn3 and Ag5Zn8 Intermetallic Compounds

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.871.254 ◽

2021 ◽

Vol 871 ◽

pp. 254-263

Author(s):

Zhan Cheng ◽

Guan Xing Zhang ◽

Wei Min Long ◽

Svitlana Maksymova ◽

Jian Xiu Liu

Keyword(s):

First Principles ◽

Density Functional ◽

Elastic Anisotropy ◽

Constant Density ◽

Mulliken Population ◽

Covalent Bonds ◽

Functional Theory ◽

The Density Functional Theory ◽

Anisotropy Index ◽

Ionic Bonds

The first-principles calculations by CASTEP program based on the density functional theory is applied to calculate the cohesive energy, enthalpy of formation, elastic constant, density of states and Mulliken population of Ag3Sn、AgZn3 and Ag5Zn8. Furthermore, the elastic properties, bonding characteristics, and intrinsic connections of different phases are investigated. The results show that Ag3Sn、AgZn3 and Ag5Zn8 have stability structural, plasticity characteristics and different degrees of elastic anisotropy; Ag3Sn is the most stable structural, has the strongest alloying ability and the best plasticity. AgZn3 is the most unstable structure, has the worst plasticity; The strength of Ag5Zn8 is strongest, AgZn3 has the weakest strength, the largest shear resistance, and the highest hardness. Ag5Zn8 has the maximum Anisotropy index and Ag3Sn has the minimum Anisotropy index. Ag3Sn、AgZn3 and Ag5Zn8 are all have covalent bonds and ionic bonds, the ionic bonds decrease in the order Ag3Sn>Ag5Zn8>AgZn3 and covalent bonds decreases in the order Ag5Zn8>Ag3Sn>AgZn3.

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Hole Transfer in Open Carbynes

Materials ◽

10.3390/ma13183979 ◽

2020 ◽

Vol 13 (18) ◽

pp. 3979

Author(s):

Constantinos Simserides ◽

Andreas Morphis ◽

Konstantinos Lambropoulos

Keyword(s):

Density Functional Theory ◽

Ground State ◽

Density Functional ◽

State Energy ◽

Frequency Content ◽

Hydrogen Atoms ◽

Functional Theory ◽

Transfer Rates ◽

Transfer Integrals ◽

End Groups

We investigate hole transfer in open carbynes, i.e., carbon atomic nanowires, using Real-Time Time-Dependent Density Functional Theory (RT-TDDFT). The nanowire is made of N carbon atoms. We use the functional B3LYP and the basis sets 3-21G, 6-31G*, cc-pVDZ, cc-pVTZ, cc-pVQZ. We also utilize a few Tight-Binding (TB) wire models, a very simple model with all sites equivalent and transfer integrals given by the Harrison ppπ expression (TBI) as well as a model with modified initial and final sites (TBImod) to take into account the presence of one or two or three hydrogen atoms at the edge sites. To achieve similar site occupations in cumulenes with those obtained by converged RT-TDDFT, TBImod is sufficient. However, to achieve similar frequency content of charge and dipole moment oscillations and similar coherent transfer rates, the TBImod transfer integrals have to be multiplied by a factor of four (TBImodt4times). An explanation for this is given. Full geometry optimization at the B3LYP/6-31G* level of theory shows that in cumulenes bond length alternation (BLA) is not strictly zero and is not constant, although it is symmetrical relative to the molecule center. BLA in cumulenic cases is much smaller than in polyynic cases, so, although not strictly, the separation to cumulenes and polyynes, approximately, holds. Vibrational analysis confirms that for N even all cumulenes with coplanar methylene end groups are stable, for N odd all cumulenes with perpendicular methylene end groups are stable, and the number of hydrogen atoms at the end groups is clearly seen in all cumulenic and polyynic cases. We calculate and discuss the Density Functional Theory (DFT) ground state energy of neutral molecules, the CDFT (Constrained DFT) “ground state energy” of molecules with a hole at one end group, energy spectra, density of states, energy gap, charge and dipole moment oscillations, mean over time probabilities to find the hole at each site, coherent transfer rates, and frequency content, in general. We also compare RT-TDDFT with TB results.

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Large H2O solubility in dense silica and its implications for the interiors of water-rich planets

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1917448117 ◽

2020 ◽

Vol 117 (18) ◽

pp. 9747-9754 ◽

Cited By ~ 2

Author(s):

Carole Nisr ◽

Huawei Chen ◽

Kurt Leinenweber ◽

Andrew Chizmeshya ◽

Vitali B. Prakapenka ◽

...

Keyword(s):

Density Functional ◽

High Pressures ◽

Density Functional Theory Calculations ◽

Mutual Solubility ◽

Hydrogen Atoms ◽

Functional Theory ◽

Geochemical Cycle ◽

High Pressures And Temperatures ◽

State Of Matter ◽

Formula Type

Sub-Neptunes are common among the discovered exoplanets. However, lack of knowledge on the state of matter in H2O-rich setting at high pressures and temperatures (P−T) places important limitations on our understanding of this planet type. We have conducted experiments for reactions between SiO2 and H2O as archetypal materials for rock and ice, respectively, at high P−T. We found anomalously expanded volumes of dense silica (up to 4%) recovered from hydrothermal synthesis above ∼24 GPa where the CaCl2-type (Ct) structure appears at lower pressures than in the anhydrous system. Infrared spectroscopy identified strong OH modes from the dense silica samples. Both previous experiments and our density functional theory calculations support up to 0.48 hydrogen atoms per formula unit of (Si1−xH4x)O2 (x=0.12). At pressures above 60 GPa, H2O further changes the structural behavior of silica, stabilizing a niccolite-type structure, which is unquenchable. From unit-cell volume and phase equilibrium considerations, we infer that the niccolite-type phase may contain H with an amount at least comparable with or higher than that of the Ct phase. Our results suggest that the phases containing both hydrogen and lithophile elements could be the dominant materials in the interiors of water-rich planets. Even for fully layered cases, the large mutual solubility could make the boundary between rock and ice layers fuzzy. Therefore, the physical properties of the new phases that we report here would be important for understanding dynamics, geochemical cycle, and dynamo generation in water-rich planets.

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