Ge-doped (4,4) armchair single-walled boron phosphide nanotube as a semiconductor: a computational study

Abstract  

Density functional theory (DFT) calculations were performed to investigate the electronic structure properties of Ge-doped boron phosphide nanotubes (BPNTs) as a semiconductor at the B3LYP/6-31G* level of theory in order to evaluate the influence of Ge doping on (4,4) armchair BPNTs. We extended the DFT calculations to predict the electronic structure properties of Ge-doped boron phosphide nanotubes, which are very important for production of solid-state devices and other applications. The isotropic (CS^I) and anisotropic (CS^A) chemical shielding parameters for the sites of various ¹¹B and ³¹P atoms, and the quadrupole coupling constant (C _Q) and asymmetry parameter (η _Q) at the sites of various ¹¹B nuclei, were calculated in pristine and Ge-doped (4,4) armchair BPNT models. The calculations indicated that, in these two forms of Ge-doped BPNTs, the binding energies are not attractive and do not characterize a chemisorption process. In comparison with the pristine model, the band gap of the two forms of Ge-doped BPNTs is reduced and increases their electrical conductance. The dipole moments of the Ge-doped BPNT structures show notable changes with respect to the pristine model. The nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) results show that the Ge_B model is a more reactive material than the pristine or Ge_P model.     

Theoretical studies of structural and electronic properties of AlnAsn clusters

We present theoretical results of size dependent structural, electronic, and optical properties of ligand‐free stoichiometric Al_nAs_n clusters of zinc‐blende modification. The investigation is done using a simplified parametrized linear combination of atomic orbital–density functional theory‐local density approximation–tight‐binding (LCAO–DFT–LDA–TB) method and consider clusters with n up to around 100. Initial structures have assumed as spherical parts of infinite zinc‐blende structure and then allowed to relax to the closest local‐energy‐minimum structure. We analyze the radial distributions of atoms, Mulliken populations, electronic energy levels (in particular, HOMO and LUMO), bandgap, and stability as a function of size and composition. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Röntgenographische Untersuchungen im System: Vanadin-Arsen-Kohlenstoff

Zusammenfassung Zwei neue binäre Vanadinarsenide werden identifiziert: V₅As₃ mit W₅Si₃-Struktur (T1) und V_1,5As, dessen Elementarzelle bestimmt wird. Im Dreistoff V–As–C werden zwei ternäre Phasen sichergestellt: V₅As₃C_0,7 mit teilweise aufgefüllter Mn₅Si₃-Struktur und V₂AsC mit Cr₂AlC-Struktur (H-Phase).

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Two new binary vanadium arsenides have been identified: V₅As₃ with W₅Si₃-structure (T1) and V_1,5As, of which the unit cell is determined. Two ternary phases were found in the ternary system V–As–C: V₅As₃C_0·7 having partially filled Mn₅Si₃-structure; V₂AsC cristallizes with the Cr₂AlC-type (H-phase).

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Mit 1 Abbildung     

Die schwingungsspektren einiger pentadeuterophenylsiliciumverbindungen

The vibrational spectra of C₆D₅SiX ₃ (X=H, Cl, Br), (C₆D₅)₂SiCl₂, (C₆D₅)₃SiCl, and Si _n (C₆D₅)_2n (n=4, 5) are reported and assigned. The C₆H₅/C₆D₅ isotopic shifts in the lower frequency region (100–600 cm^–1) are used to elucidate vibrational coupling effects, which occur between silicon-phenyl and silicon-halogen or silicon-silicon modes.

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Herrn Prof. Dr.H. Grubitsch mit den besten Wünschen zum 70. Geburtstag gewidmet.     

Weitere Reaktionen von 1,3-Dichlordisilazanen und 1,3-Dichlordisiloxanen

Zusammenfassung Spezielle Umsetzungen von 1,3-Dichlordisilazanen werden beschrieben. Die Umsetzung mit einem bestimmten Amin führte zu einer SiNSiN-Verbindung mit 6 verschiedenen Substituenten (I; Rk. 1). Analog bildeten sich mit Hydrazinen Bis(hydrazino)-disilazane der Strukturgruppe NNSiNSiNN (II, III; Rk. 2). Mit Äthylendiamin konnte ein Si₂N₃C₂-Siebenringsystem (IV), mit Bis(trimethylsilyl)harnstoff ein Sechsringsystem Si₂N₃C (VI), mit Diphenylsilandiol das Cyclotrisildioxazan-Sechsringsystem (VIII, IX) aufgebaut werden. 1,3-Dichlordisiloxan ergab in ähnlichen Umsetzungen erstmalig ein Si₂N₂OC₂-Siebenringsystem (V) und ein Si₂N₂OC-Sechsringsystem (VII).

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New reactions of 1.3-dichlorodisilazanes and 1.3-dichlorodisiloxanes. (chemistry of silicon-nitrogen compounds, XCVIII)

Special reactions of 1.3-dichlorodisilazanes give a) with a special amine a SiNSiN-compound with 6 different substituents (I; equ. 1); b) with hydrazines bis(hydrazino)disilazanes of the structural unit NNSiNSiNN (II, III; equ. 2); c) with ethylenediamine a novel Si₂N₃C₂-sevenmembered ring system (IV); d) with bis(trimethylsilyl)urea a sevenmembered ring system Si₂N₃C (VI); e) with diphenylsilanediol the cyclotrisildioxazane ring system (VIII, IX). Analogous reactions of 1.3-dichlorodisiloxanes lead to the novel sevenmembered ring system Si₂N₂OC₂ (V) and to the sixmembered Si₂N₂OC-ring system (VII).

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97. Mitt.:U. Wannagat, L. Gerschler undH. J. Wismar, Mh. Chem.102, 1834 (1971).

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Vorläufige Mitt. von Teilergebnissen:U. Wannagat, Angew. Chem.77, 626 (1965); Pure appl. Chem.13, 262 (1966).

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Mit Auszügen aus den DissertationenE. Bogusch, Techn. Hochschule Graz 1966, undF. Rabet, Techn. Univ. Braunschweig 1971, sowie nach Arbeiten vonP. Geymayer, Techn. Hochschule Graz 1965.     

Thermodynamic Properties of Liquid n-Pentadecane

Abstract

This paper reports experimental results concerning the isobaric heat capacity C_p of Liquid n-pentadecane as a function of pressure (up to 100 MPa) and temperature (313.15 to 373.15 K). The measurements were performed with a modified C80 SETARAM calorimeter based on the Calvet principle. These calorimetric data, combined with density data, were used to evaluate derived thermophysical properties such as the isochoric heat capacity C_v , the isentropic compressibility k_s and the speed of sound u in the same ranges of pressure and temperature. The pressure-temperature behaviour of these properties was then discussed as a model for simple organic liquids.     

A combined X-ray crystallography and theoretical study of PPh2CH2SPh and PPh2C6H4SMe ligands

Abstract

The solid-state structures of compounds PPh₂CH₂SPh (1) and PPh₂C₆H₄SMe (2) were determined by single crystal X-ray diffraction. Experimental results on the molecular structures of compounds 1 and 2 were supported by Hirshfeld surface analysis and Density Functional Theory (DFT). The computed values calculated at DFT level using B3LYP function with 6-311++G (3df, 3pd) (P, S) and 6-31G* (C, H) basis sets are in good agreement with the experimental results.     

High Magnetic Moments in Manganese‐Doped Silicon Clusters

We report on the structural, electronic, and magnetic properties of manganese‐doped silicon clusters cations, Si_nMn⁺ with n=6–10, 12–14, and 16, using mass spectrometry and infrared spectroscopy in combination with density functional theory computations. This combined experimental and theoretical study allows several structures to be identified. All the exohedral Si_nMn⁺ (n=6–10) clusters are found to be substitutive derivatives of the bare Si_n+1⁺ cations, while the endohedral Si_nMn⁺ (n=12–14 and 16) clusters adopt fullerene‐like structures. The hybrid B3P86 functional is shown to be appropriate in predicting the ground electronic states of the clusters and in reproducing their infrared spectra. The clusters turn out to have high magnetic moments localized on Mn. In particular the Mn atoms in the exohedral Si_nMn⁺ (n=6–10) clusters have local magnetic moments of 4 μ_B or 6 μ_B and can be considered as magnetic copies of the silicon atoms. Opposed to other 3d transition‐metal dopants, the local magnetic moment of the Mn atom is not completely quenched when encapsulated in a silicon cage.     

A Combined Experimental and Computational Study of Linear Ruthenium(II) Coordination Oligomers with End‐Capping Organic Redox Sites: Insight into the Light Absorption and Charge Delocalization

Two series of linear ruthenium coordination oligomers, [(Ntpy)Ru_n(tppz)_n?1(tpy)]²ⁿ⁺ (mono‐Ntpy series, n=1–3) and [(Ntpy)₂Ru_n(tppz)_n?1]²ⁿ⁺ (bis‐Ntpy series, n=1–3) have been prepared, where Ntpy is the capping ligand 4′‐di‐p‐anisylamino‐2,2′:6′,2′′‐terpyridine, tppz is tetra‐2‐pyridylpyrazine, and tpy is 2,2′:6′,2′′‐terpyridine. The electrochemical measurements evidence oxidation events from both the amine segments and the metal centers and reduction waves from tppz and the capping ligands. Both series complexes display much enhanced light absorption with respect to model complexes without terminal amine units. Density functional theory (DFT) calculations have been performed on both series and time‐dependent DFT (TD‐DFT) calculations have been performed on the bis‐Ntpy‐series compounds (n=1–4) to characterize their electronic structures and excited states and predict the electronic properties of long‐chain polymers. Upon one‐electron oxidation, the mono‐Ntpy‐series monoruthenium and diruthenium complexes display N⁺‐localized transitions and metal‐to‐nitrogen charge‐transfer (MNCT) transitions in the near‐infrared (NIR) region. DFT and TD‐DFT computations on the one‐electron‐oxidized forms of the mono‐Ntpy‐series compounds (n=1–4) provide insight into the nature of the MNCT transitions and the degree of charge delocalization.     

A theoretical investigation on doping superalkali for triggering considerable nonlinear optical properties of Si12C12 nanostructure

In this work, we designed a series of superalkali‐doped Si₁₂C₁₂ nanocage M₃O@Si₁₂C₁₂ (M = Li, Na, K) with donor–acceptor framework. Density functional theory calculations demonstrated that the HOMO–LUMO gap of the complexes conspicuously narrowed with increase of atomic number of the alkali metal, the value decreased from 5.452 eV of pure Si₁₂C₁₂ nanocage to 3.750, 2.984, and 2.634 eV of Li₃O@Si₁₂C₁₂, Na₃O@Si₁₂C₁₂, and K₃O@Si₁₂C₁₂, respectively. This finding shows that the pristine Si₁₂C₁₂ cluster could be transformed to n‐type semiconductor by introduction of the superalkali M₃O. We also showed that the superalkali doping remarkably enhanced the first hyperpolarizability of Si₁₂C₁₂. Among the studied systems, K₃O@Si₁₂C₁₂ not only has the narrowest gap but also has the strongest nonlinear optical (NLO) properties, its first hyperpolarizability reached as high as 21695 a.u. The striking results presented in this work will be beneficial for potential applications of the Si₁₂C₁₂‐based nanostructure in the electronic nanodevices and high‐performance NLO materials. © 2017 Wiley Periodicals, Inc.     

DFT studies on TinC2n (n=1–6) clusters

The geometric configurations and electronic structures of the Ti_nC_2n (n=1–6) clusters were studied by using the quantum chemical ab initio density functional theory (DFT) method. Our studies showed that these Ti_nC_2n (n=1–6) could grow gradually to form cyclic clusters through the subunits TiC₂ bonding to each other by C C or Ti C bond. The result could explain the existing experimental fact. The studies might also be helpful to the knowledge of the formation mechanism of the Met‐Cars. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 71: 313–318, 1999     

A theoretical study of the dependence of the ASxSi6−x cluster structures and properties on composition

The effect of the composition ratio between arsenic and silicon atoms on the structures and properties of As_xSi_6?x (x = 0–6) have been systematically investigated using the density functional theory at the B3LYP/6‐311+G* level. The As_xSi_6?x clusters prefer substitutional rather than attaching structures; the Si‐rich clusters favor Si₆‐like structures, whereas the As‐rich clusters prefer As₆‐like structures. The As atoms locating at the framework may explain the difficulty of removal of arsenic impurities from polycrystalline silicon. In general, the average binding energies gradually decrease, implying the As_xSi_6?x clusters become increasingly unstable as x increases. Both the HOMO‐LUMO gaps and the As‐dissociation energies present a strong even–odd alternation, implying alternating chemical stability, with the even x members being more stable than the odd ones. The dissociation energies of an As atom from As_xSi_6?x are: 3.07, 2.84, 1.84, 2.52, 1.86, and 2.85 eV, for x = 1–6, respectively, and 3.80, 3.08, 2.64, 3.01, 2.93, 3.16 eV for Si (x = 0–5). These dissociation energy results should provide a useful reference for further experimental investigations. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Monoelemental polymers: Structure and properties

Monoelemental polymers with various chemical constitutions and different spatial structures (linear Te _n , Se _n , and S _n ; planar graphite C _n , black phosphorus P _n , As _n , Sb _n , and Bi _n ; and chemically bonded three-dimensional diamond C _n , B _n , Si _n , and Ge _n ) were considered and categorized as a class of covalent macromolecular compounds. Quantitative expressions relating the thermal (melting point, thermal expansion coefficient, heat conductivity) and elastic (microhardness, bulk compression modulus of elasticity) properties of polymers to the energy of intra-and intermolecular interactions and the equilibrium length of chemical bonds in the crystalline and glassy states are given. A numerical correlation between the spatial structure of polymers and their thermal and elastic properties was obtained. The hypothetical melting point of diamond at normal pressure was calculated as T _f = 3155 K.     

An Approach to Mixed PnAsm Ligand Complexes

The reaction of a P₄ butterfly complex with yellow arsenic yields the largest mixed P_nAs_m ligand complexes synthesized to date. [{Cp′′′Fe(CO)₂}₂(μ,η^1:1‐P₄)] reacts with As₄ to yield [{Cp′′′Fe}₂(μ,η^4:4‐P_nAs_4‐n)] and [Cp′′′Fe(η⁵‐P_nAs_5‐n)]. Mass spectrometry together with NMR spectroscopy and X‐ray crystallography give clear evidence about the arrangement of the E positions within the cyclo‐E₅ and E₄ moieties of the products. Moreover, the results of DFT calculations agree well with the experimental determined outcomes. By coordinating the E₄ complex [{Cp′′′Fe}₂(μ,η^4:4‐P_nAs_4‐n)] with CuCl, a rearrangement of the E positions occurs in favor with a preferred phosphorus coordination towards copper atoms in the resulting 1D polymeric chain.     

A study of the electronic structure of polyvinylsiloxane (CH<Superscript>2</Superscript>CHSiO<Subscript>1.5</Subscript>)<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> by X-ray photoelectron spectroscopy and quantum chemical modeling in the DFT approximation

The electronic structure of polyvinylsiloxane polymeric chains (Si₂O₃(CHCH₂)₂)_n is studied by X-ray photoelectron spectroscopy and quantum chemistry in the DFT approximation. The binding energy of C and O ls electrons occupying inequivalent positions in the polymer coincides within the experimental accuracy. The binding energies for C and O (284.9 eV and 532.4 eV) and for Si2p-electrons (102.7 eV) well agree with the values for related compounds. The experimental data for the binding energy are reproduced in HF and DFT calculations only with the extended 6–311**(d) basis set. The highest occupied levels of the polymer are fy orbitals of vinyl groups     

Techniques used to study the chemistry of gas phase elemental clusters

Recent studies of the chemistry of elemental clusters (such as C _n , Si _n , and Fe _n ) in the gas phase have revealed a number of fascinating results. This review article discusses and compares the various techniques that have been used to investigate the chemical properties of gas phase elemental clusters. Examples are provided of the often complimentary information that can be obtained from the different methods.     

计算机模拟铌原子簇的稳定构型和能量性质

采用密度泛函(DFT)方法结合全局优化"Basin-Hopping"算法研究了铌原子簇: 对于Nb小簇n＝2～6我们用密度泛函方法计算了它们的稳定几何构型和电子结构, 通过拟合计算结果构造铌原子簇势能函数, 并利用该函数和全局优化"Basin-Hopping"算法得到较大铌原子簇(n＝7～20)能量极小的结构. 计算结果表明与实验及其它计算结果相一致.     

On the Constant Pressure Specific Heat CP of a Simple Fluid

Abstract

Calculation of C_P from a model soft-core equation of state reveals a line in the phase diagram on which C_P is equal to its zero pressure value C _{P 0} . This line commences on the temperature axis where the second virial coefficient has a point of inflexion. At higher temperatures (and pressures) C_P falls below C _{P 0} . The detailed behaviour of C_P is presented via contour maps, illustrating the effects of changing the exponent N(= 3/n, where n is the repulsive potential exponent) which parameterizes the model. For soft-core fluids at high temperatures C_P deviates only slightly from the ideal gas value over a wide range of temperature and density, in marked contrast to the behaviour of hard-core models.     

A High Pressure Study on NH4Pb2Br5 Type Compounds Part II: Electronic Structure and Changes under High Pressure

In this work, we present a theoretical study (based on DFT‐calculations) of the electronic properties of compounds crystallising in a NH₄Pb₂Br₅ type structure in a wide pressure range. The main focus of this study is to elucidate the nature of bonding of the ns²‐cations at ambient and elevated pressure. For a better understanding of the structure and bonding, the DOS of these compounds are evaluated and discussed on the basis of a simple model assuming mainly ionic interactions. The calculations are complemented by an orbital analysis using the crystal orbital Hamilton population (COHP) and an analysis of the electronic density topology with the electron localisation function (ELF). Structural and theoretical investigations give results that are in excellent agreement: The DFT‐calculations confirm the existence of bonding interactions between the ns²‐cations at elevated pressure. Our study indicates that the “character” of the additional electron pair changes with increasing pressure from nonbonding to bonding in agreement with a simple model system of two interacting ns²‐cations.