Structures and Electronic Properties of Ni–Al Alloy Clusters from First-Principles Calculations

Using the density functional theory calculations with the PBE exchange–correlation energy functional, we have studied the low-energy structures and electronic properties of Ni–Al alloy clusters for adsorbing or doping an aluminum atom to Ni_n (n = 13, 19, 23, 26, 29 and 55) clusters. The most stable structures of Ni_nAl are viewed as adding an Al atom at the hollow triangle and rhombus site of the icosahedron (n = 13, 55) and double-icosahedron (n = 19, 23, 26 and 29) structures, respectively. For Ni_n?1Al, it can be seen that an Al atom gradually moves from surface (n = 13, 19, 23 and 26) to the interior site (n = 29, 55) in the most stable structures. The electronic properties of the Ni–Al alloy clusters including binding energies, magnetic properties, charge transfer and density of states have also been studied.     

Structural,Electronic and Optical Properties of the Monoclinic α-CoV_2O_6

First-principles calculations based on density functional theory are performed to investigate the structural,electronic and optical properties of monoclinic α-Co V2O6.Firstly,the geometry structures obtained by geometry optimization are consistent with the experimental values.Then,the energy band structure is studied using both GGA and GGA+U methods.It is found that the on-site Coulomb repulsion of the Co 3d orbital plays a key role in describing the electronic properties of α-Co V2O6,and is necessary to open the energy band gap.According to the partial density of states(PDOS),significant Co–O and V–O hybridizations are observed in the valence and conduction bands,respectively.Furthermore,the Co–O and V–O bonds are found to have significant covalent characters.Below the absorption threshold ~1.9 e V,no absorption can be detected.However,there exists a strong and wide absorption band in the energy range from 1.9 to 11 e V.Such novel optical properties imply that the α-Co V2O6 may have some potential optical applications.     

Structural Properties and Thermal Behavior of Li2CO3–BaCO3 System by DTA,TG and XRD Measurements

The binary system Li₂CO₃–BaCO₃ was studied by means of differential thermal analysis (DTA), thermogravimetry (TG) and X-ray phase analysis. The composition of carbonate and CO₂ partial pressure influence on the thermal behavior of carbonate were examined. It was shown that lithium carbonate does not form the substitutional solid solution with barium carbonate, however the possible formation of diluted interstitial solid solutions is discussed. Above the melting temperature the mass loss is observed on TG curves. This loss is the result of both decomposition of lithium carbonate and evaporation of lithium in Li₂CO₃–BaCO₃ system. Increase of CO₂ concentration in surrounding gas atmosphere leads to slower decomposition of lithium carbonate and to increase the melting point. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal and Structural Investigation of the Reaction Between 1,2-propanediol and Co(NO3)2⋅6H2O

The results of an investigation concerning there action between 1,2-propanediol and Co(NO₃)₂⋅ 6H₂O, leading to a complex containing the lactate anion (L) as ligand are presented. The obtained solid homopolynuclear coordination compound[Co₂(OH)₂L₂(H₂O)₂⋅0.5H₂O]_n, has been investigated by thermal analysis, electronic and IR spectroscopy and magnetic methods. Cobalt oxide obtained by thermal decomposition of this coordinative compound was characterized by IR and X-ray spectroscopy. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal and Structural Investigation of The Reaction Between 1,2-propanediol and Ni(NO3)2⋅6H2O

The authors present the results of an investigation concerning the reaction between 1,2-propanediol and Ni(NO₃)₂6H₂O, leading to a complex containing as ligand the lactate anion (L), suggesting that the oxidation of 1,2-propanediol occurs at the primary hydroxyl group. The obtained solid homopolynuclear combination, [Ni₂(OH)₂L₂(H₂O)₂0.5H₂O]_n, has been investigated by thermal analysis, electron and IR spectroscopy,and magnetic methods. Nickel oxide obtained by thermolysis of this complex compound was characterized by IR, X-ray spectroscopy and elemental analysis. All the investigations lead to the conclusion that the complex compound is characterized by pseudooctahedral configuration of the nickel(II) ion. Thermal analysis of the homopolynuclear complex compound enabled to prove the thermal decomposition mechanism.This revised version was published online in November 2005 with corrections to the Cover Date.     

DFT Studies on the Stoichiometric Thorium Oxide Clusters(ThO_2)_n(n = 1～5): Electronic and Structural Properties

Density functional theory(DFT) calculations are performed to investigate the electronic and structural properties of the stoichiometric thorium oxide clusters(ThO_2)_n-/0(n = 1～5). Generalized Koopmans' theorem is applied to predict the vertical detachment energies(VDEs)which are used to simulate the anionic photoelectron spectra(PES). Molecular orbital analyses are performed as well to analyze the chemical bonding in these thorium oxide clusters. The results show that the ground states of(ThO_2)_n-/0(n = 1～5) clusters prefer the low-spin structures. With increasing of the cluster size(n), the structure parameters of(ThO_2)_n-/0(n = 1～5) gradually evolve toward bulk thorium oxide species. It shows that both the coordination number and the average bond length increase gradually in(ThO_2)_n-/0(n = 1～5) to approach that of ThO2 bulk. What's more, the vibration frequencies of Th=O double bonds are found to be decreasing along with the increased cluster size.     

Structural,Electronic and Magnetic Properties of Co_nO(n = 2～10) Clusters: A Density Functional Study

The structural, electronic, and magnetic properties of Co_nO(n = 2～10) clusters have been systematically investigated within the framework of the generalized gradient approximation density functional theory. The results indicate that the O atom occupies the surface-capped position on Co_nO(n = 2～10) clusters. The stabilities of the host clusters are improved by adding one O atom. Maximum peaks of the second-order difference energy of the ground-state Co_nO clusters are found at n = 3, 6 and 8, indicating higher stability than their neighboring clusters. Compared with corresponding pure Con clusters, the O-doped cobalt clusters have larger gaps between the HOMO and LUMO energy levels, indicating their higher chemical stabilities. In addition, the doping of O atom exhibits different influence on the magnetism of the clusters. This is also further investigated by the local magnetic moment, deformation charge density and partial local density of states analysis.     

Thermal Decomposition Mechanism, Thermodynamical and Quantum Chemical of Properties [Pb(NTO)2⋅(H2O)]

The single crystal of lead salt of 3-nitro-1,2,4-triazol-5-one (NTO), [Pb(NTO)₂(H₂O)] was prepared and its structure was determined by a four-circle X-ray diffractometer. The crystal is monoclinic, its space group is P2₁/n with crystal parameters of a=0.7262(1) nm, b=1.2129(2) nm, c=1.2268(3) nm, =90.38(2)°, V=1.0806(2) nm³, Z=4, D_c=2.97 g cm^–3, µ=157.83cm^–1, F(000)=888. The final R is 0.027. By using SCF-PM3-MO method we obtained optimized geometry for [Pb(NTO)₂H₂O] and particularly positions for hydrogen atoms. Through the analyses of MO levels and bond orders it is found that Pb atom bond to ligands mainly with its 6p_z and 6p_y AOs. The thermal decomposition experiments are elucidated when [Pb(NTO)₂H₂O] is heated, ligand water is dissociated first and NO₂ group has priority of leaving. Based on the thermal analysis, the thermal decomposition mechanism of [Pb(NTO)₂H₂O] has been derived. The lattice enthalpy and its lattice energy were also estimated.This revised version was published online in November 2005 with corrections to the Cover Date.     

Preparation and Properties of(BEDT-TTF)_2Br3H_2O Salt

Chargetransfersaltsoforganicdonormoleculehis(ethylenedithio)tetrathiafulvalene(BEDT--TTF)havebeenofgreatinterestduringthelastdecades,becauseofthewiderangeofphysicalpropertieswhichtheyexhibitl'2'3.Recently,ourgrouppreparedandstudiedorganicconductorsonthebaseofNi(dmit)2anions(dmit=l,3-dithiol-2-thione4,5-dithiolate)withEDA4(2-diethylamino-l,3-dithiolanylium),andfoundedthatthereweremanySScontactswhichareshorterthanthesumofvanderWaalsradii(3.70A)betweencanonsandanions.Theresultspromptedustoi…     

Synthesis,Thermal Properties,and Radiolysis of Poly(Cyclohexyl α-Chloroacrylate)

Cyclohexyl α-chloroacrylate (CCA) was polymerized by radical anionic and γ-radiation initiation. The anionic polymerization of cyclohexyl α-chloroacrylate gave moderately isotactic polymer in toluene and syndiotactic-rich polymer in THF. Poly(cyclohexyl α-chloroacrylate) (PCCA) was found to undergo two-stage weight loss in thermogravimetric analysis, and the first-stage weight loss was attributed to the lactonization reaction. PCCA degraded under γ-radiation, and the radiation yields of crosslinking and scission, G _x and G _s, were 0.6 and 3.8, respectively.     

Synthesis,Structure, and Properties of Cesium Polyuranate [Cs2(H2O)3][(UO2)6O3(OH)8]·2H2O

Russian Journal of General Chemistry - Cesium uranate [Cs2(Н2О)3][(UO2)6O3(OH)8]·2H2O was obtained by reacting hydrated uranium(VI) oxide UO3·2.25H2O with a cesium nitrate...     

Controlling Electronic Events Through Rational Structural Design in Subphthalocyanine–Corrole Dyads: Synthesis,Characterization, and Photophysical Properties

Porphyrinoids are considered perfect candidates for their incorporation into electron donor–acceptor (D–A) arrays due to their remarkable optoelectronic properties and low reorganization energies. For the first time, a series of subphthalocyanine (SubPc) and corrole (Cor) were covalently connected through a short-range linkage. SubPc axial substitution strategies were employed, which allowed the synthesis of the target molecules in decent yields. In this context, a qualitative synthetic approach was performed to reverse the expected direction of the different electronic events. Consequently, in-depth absorption, fluorescence, and electrochemical assays enabled the study of electronic and photophysical properties. Charge separation was observed in cases of electron-donating Cors, whereas a quantitative energy transfer from the Cor to the SubPc was detected in the case of electron accepting Cors.     

Theoretical Study of the Structural,Electronic, and Magnetic Properties of Zirconium-doped Aluminum Clusters:Al_nZr(n = 1～14)

The geometrical structures, stabilities, electronic and magnetic properties of Al_nZr(n = 1~14) clusters have been systematically investigated using density functional theory. It is found that for the optimized clusters the zirconium atom prefers to remain on the surface, and the growth patterns are organized as follows: Zr substituted Al_(n+1) clusters or Zr capped Aln clusters as well as Al added Al_(n-1)Zr clusters. All doped clusters exhibit relatively larger average binding energies and magnetic behaviors compared with pure Al_(n+1) counterpart. The calculated fragmentation energies and second-order difference of energies exhibit pronounced odd-even alternation behavior as a function of the cluster size when n = 3~13. In all Al_nZr clusters, there exits internal hybridization in both Al and Zr atoms and charge transfer from Al to Zr atom, which reflects the strong interactions between the two kinds of atoms. The magnetic property analysis shows that the 4d electrons of Zr atom are the main origin for cluster magnetism.     

Synthesis, Characterization, and Physical Properties of Two Trinuclear, Mixed-Valence Species of Type [μ3-OMnIIMnIII 2(O2CCF3)6(R)3] (R=H2O, CH3COOH)

The preparation and characterization of two new mixed-valence, trinuclear species, [Mn₃O(O₂CCF₃)₆(H₂O)₃]CF₃COOH4/3H₂O (1) and [Mn₃O(O₂CCF₃)₆(CH₃COOH)₃] (2), is reported. Compound 1 crystallizes in the triclinic space group, P¯1 (No. 2), with the parameters, a=12.3131(9) Å, b=12.4427(9) Å, c=12.965(1) Å, =72.593(4)°, =73.453(5)°, =68.345(4)°, V=1727.2(2) ų, and Z=2. A total of 14060 reflections were collected in the range 1.6827.52°. The final weighted and non-weighted agreement indices, R1=0.0589 and wR2=0.1445 were based on a total of 6953 unique reflections with an R _int value of 0.0542. Compound 2 crystallizes in the monoclinic space group, P2₁/n (No. 14), with the parameters, a=12.876(3) Å, b=12.212(4) Å, c=17.732(4) Å, =100.40(3)°, V=3640.4(1) ų, and Z=4. A total of 32197 reflections were collected in the range 1.7227.13°. The final weighted and non-weighted agreement factors, R1=0.0647 and wR2=0.1609 were based on a total of 8018 unique reflections with an R _int value of 0.0462. An investigation of the physical properties revealed that both compounds display an intermediate ground state of S=3/2 as a consequence of intramolecular antiferromagnetic coupling. The magnetic data for compound 1 was best fit to the parameters g=2.09, J=–5.5 cm^–1, J=–3.4 cm^–1, and D _Mn(III)=–4.5 cm^–1; the data for compound 2 was best fit to the parameters g=2.10, J=–2.9 cm^–1, J=–5.5 cm^–1, and D _Mn(III)=–4.5 cm^–1.     

Evolution of Structural, Electronic and Optical Properties of Monoclinic ZrO2 under High Pressure： A First Principles Study

The structural, electronic and optical properties of the monoclinic ZrO2 were studied by ab initio calculations based on the density functional theory and pseudopotential method. The calculated lattice parameters and band gap are in agreement with the experimental and other theoretical values. The evolution of lattice parameters and electronic properties were illustrated under high pressure. Meanwhile, the optical properties, such as adsorption coefficients, imaginary part of dielectric function, and energy loss function, were investigated under both ambient and high pressures.     

Structural,spectral and potentiometric characterization,and antimicrobial activity studies of [Zn(phen)2(cnge)(H2O)](NO3)2 · H2O

An octahedral Zn complex with o-phenanthroline (o-phen) and cyanoguanidine (cnge) has been synthesized and characterized. The crystal structural data show the formation of a ZnN₅O core where the metal coordinates to two mutually perpendicular o-phenanthrolines as bidentate ligands [Zn–N bond lengths in the 2.124(2)–2.193(2)?Å range], the cyanide nitrogen of a cnge [d(Zn–N)?=?2.092(2)?Å, ∠(Zn–N–C)?=?161.1(2)°], and a water molecule [d(Zn–Ow)?=?2.112(2)?Å]. Spectral data (FT-IR, Raman, and fluorescence) and speciation studies are in agreement with the structure found in the solid state and the one proposed to exist in the solution. To evaluate the changes in the microbiological activity of Zn, antibacterial studies were carried out by observing the changes in minimum inhibitory concentration of the complex, the ligands, and the metal against five different bacterial strains. The antibacterial activity of Zn improved upon complexation in three of the tested strains.     

Photoluminescence Spectra and Crystallization of θ-Al2O3 and α-Al2O3 from AlOOH-Fe(NO3)3 Gels

Diphasic boehmite derived unseeded and seeded (by either -Al₂O₃, -Fe₂O₃, or Fe(NO₃)₃) alumina gel planar monoliths were examined by DTA, XRD and photoluminescence spectroscopy. Luminescence spectra enable sensitive monitoring of the - and -Al₂O₃ crystallization in heat-treated gels due to Cr³⁺ impurity traces. Fe(NO₃)₃ unlike other seeds effectively influences crystallization of both - and -Al₂O₃. The present results are interpreted as prevailing solution or Fe³⁺ ion effect on the crystallization process.     

Synthesis,Crystal Structure and Spectral Properties of [Ce(NO3)5(H2O)2]·2(Hphen)·(H2O)

A novel complex [Ce(NO3)5(H2O)2]·2(Hphen)·(H2O) (phen =1,10-phenanthroline) with formula C24H24CeN9O18 and Mr = 866.64 has been synthesized and structurally characterized by X-ray diffraction. It crystallizes in triclinic, space group Pī with a = 7.5534(2), b = 8.083(2), c = 25.8377(6) A, α = 86.847(1), β = 89.937(1), γ = 86.981(1)o, V = 1572.94(6) A3, Dc = 1.830 g/cm3, F(000) = 866, β = 1.545 cm-1 and Z = 2. The final refinement gave R = 0.0486 and wR = 0.1278 for 4852 observed reflections with I > 2σ(I). It consists of discrete [Ce(NO3)5(H2O)2]2- anion, two Hphen+ cations and a lattice water molecule. In the compound, all of the five nitrates are bidentate, and the coordination of Ce(III) is 12. The photo-luminescence of this compound was also investigated.     

Thermal and calorimetric investigations of Mg(IO3)2·nH2O (n=10, 4) and their deuterated analogues

A DTA and DSC study was made of the thermal dehydration and decomposition of Mg(IO₃)₂·4H₂O and Mg(IO₃)₂·4D₂O. The data obtained show that the dehydration takes place in one stage. The ΔH _deh ^o obtained were used to calculate ΔH _f ^o , and comparisons were made with the literature data. It was confirmed that the thermal decomposition passes through an intermediate Mg₅(IO₆)₂, which is unstable and immediately decomposes to MgO. An isotope effect is observed in both DTA and DSC curves. Thermogravimetric data on Mg(IO₃)₂·10H₂O are also presented.