Electronic and Structural Properties of Neutral, Anionic, and Cationic Rh x Cu4−x (x = 0–4) Small Clusters: A DFT Study

In this study, electronic structure, stability, and tendency to exchange electron of neutral, anionic, and cationic Rh _x Cu_4?x (x = 0–4) small clusters were investigated by density functional theory calculations. For neutral small clusters, it was found that the most stable structures of Rh₄, Rh₃Cu and Rh₂Cu₂ have distorted tetrahedral shape while the most stable structures of RhCu₃ and Cu₄ have quasi-planer shape. Adding charges to the clusters, caused shapes of the most stable structures undergo variations. Stabilities of the neutral, anionic, and cationic clusters decrease linearly with increasing the copper content. In addition, calculated chemical harnesses indicated that the small cluster with 75 % copper content has the least chemical hardness. Interestingly, prevailing number of electronegative (Rh) and electropositive (Cu) atoms in the anionic and cationic clusters coincides with high dipole moment in these species that occur at 25 and 75 % copper respectively.     

Effect of hydration on conductivity of Ba4La x Ca2 − x Nb2O11 + 0.5x (x = 0.5, 1, 1.5, 2) phases

Substitution of Ca by La in initial cubic double perovskite Ba₄(Ca₂Nb₂)O₁₁[VO]₁ allowed obtaining phases with a similar structure with a lower content of structural oxygen vacancies, Ba₄(La _x Ca_{2 ? x} Nb₂)O_{11 + 0.5x} [VO]_{1 ? 0.5x} (x = 0.5, 1, 1.5, 2). The impedance technique was used to measure the temperature dependences of conductivity in the atmosphere of dry and humid air. Transport numbers determined using the EMF method in an oxygen-air and water steam concentration cells point to the predominantly hole nature of conductivity in the high-temperature region (T > 600°C) and to predominance of proton conductivity in the low-temperature region. Activation energies of hole and proton conductivity were calculated. Thermogravimetric measurements were carried out under heating from 25 to 1000°C with simultaneous mass-spectrometric determination of evolved H₂O and CO₂. The properties of the studied Ba₄(La _x Ca_{2 ? x} Nb₂)O_{11 + 0.5x} (x = 0.5, 1, 1.5, 2) phases were compared with the earlier studied Ba_{4 ? x} La _x (Ca₂Nb₂)O_{11 + 0.5x} phases with similar lanthanum content.     

Kinetics of phase transition and thermal stability in Se80?x Te20Zn x (x?=?2, 4, 6, 8, and 10) glasses

Se_80?x Te₂₀Zn _x (x?=?2, 4, 6, 8, and 10) glasses have been prepared using conventional melt quenching technique. The kinetics of phase transformations (glass transition and crystallization) have been studied using differential scanning calorimetry (DSC) under non-isothermal condition at five different heating rates in these glasses. The activation energy of glass transition (E _t), activation energy of crystallization (E _c), Avrami exponent (n), dimensionality of growth (m), and frequency factor (K _o) have been investigated for the better understanding of growth mechanism using different theoretical models. The activation energy is found to be highly dependent on Zn concentration. The rate of crystallization is found to be lowest for Se₇₀Te₂₀Zn₁₀ glassy alloy. The thermal stability of these glasses has been investigated using various stability parameters. The values of these parameters were obtained using characteristic temperatures, such as glass transition temperature T _g, onset crystallization temperature T _c, and peak crystallization temperature T _p. In addition to this, enthalpy-released during crystallization has also been determined. The values of stability parameters show that the thermal stability increases with the increase in Zn concentration in the investigated glassy samples.     

Rubidium-cationic conductivity of Rb2−2x Ga2−x A x O4 (A = P, V, Nb, Ta) solid electrolytes

Solid solutions based on rubidium monogallate RbGaO₂ with a general formula Rb_2?2x Ga_2?x A _x O₄ (A = P, V, Nb, and Ta) are synthesized. Their crystal structure and temperature and concentration dependences of conductivity are studied. The highest rubidium-cationic conductivity is (1.8–3.9) × 10^?3 S cm^?1 at 400°C and (1.4–2.1) × 10^?2 S cm^?1 at 700°C. These results are compared with the data for rubidium monogallate doped with four-charged cations and solid solutions based on RbAlO₂.     

Lithium-cationic conductivity in the Li4 − 2x Cd x GeO4 system

The lithium-conducting solid electrolytes in the Li_{4 ? 2x} Cd _x GeO₄ (0 ≤ x ≤ 0.6) system are synthesized. Their crystal structure and temperature and concentration dependences of conductivity are studied. The specimens with the highest conductivity have a γ-Li₃PO₄-derivative structure. The solid solutions with x = 0.15–0.25 are stable at the room temperature, whereas the specimens with x ≥ 0.3 decompose yielding Li₂CdGeO₄ below 310 ± 10°C. Li_3.6Cd_0.2GeO₄ solid solution exhibits the highest conductivity (5.25 × 10^?2 S cm^?1 at 300°C). The factors, which affect the conductivity of synthesized solid electrolytes, are considered.     

NMR, DTA, and impedance spectroscopy studies of ion mobility, phase transitions, and ionic conductivity in K1 − x (NH4) x SbF4 crystals

The ion mobility, phase transitions, and ionic conductivity in the crystal phases in the KF-NH₄F-SbF₃ system were studied by NMR, DTA, and impedance spectroscopy. An analysis of the ¹⁹F and ¹H NMR spectra showed how the character of ionic motions in the fluoride and proton sublattices changed with temperature. The types and temperature ranges of ionic motions were determined. Diffusion of the fluoride and partially ammonium ions was found to be the dominant form of ionic motion in the high-temperature modifications formed as a result of phase transitions. According to the electrophysical data, the high-temperature K_{1 ? x} (NH₄) _x SbF₄ phases (0.05 ≤ x ≤ 0.75) are superionic, their conductivity reaching ～10^?2–10^?3 S/cm at 450–500 K.     

Electroconductivity of Solid Solutions Cs3–2x M x PO4 (M = Ba, Sr, Ca, Mg)

Solid solutions Cs_{3 – 2x} M _x PO₄ (M = Ba, Sr, Ca, Mg) are synthesized and their thermal behavior and electroconductivity are examined. Adding elements of Subgroup IIA of the periodic table into cesium orthophosphate shifts the phase transition, which occurs in pure Cs₃PO₄ at 450–620°, towards lower temperatures and raises the cesium cation conductivity at low temperatures. The electroconductivity of a high-temperature modification of Cs₃PO₄ is weakly dependent on the presence and concentration of such additives, which points to structural disordering of the cesium sublattice.     

Phosphates M 0.5(1 + x) 2+ Cr x Ti2 − x (PO4)3: Synthesis, structure, and catalytic properties

Complex phosphates of titanium, chromium, and metals(2+) of the general formula M_{0.5(1 + x} )Cr _x Ti_{2 ? x} (PO₄)₃ (M = Mg, Ca, Mn, Ni, Sr, Ba, and Pb) were synthesized. Their phase formation was studied by means of X-ray powder diffraction, electron probe microanalysis, differential thermal analysis, and IR spectroscopy. Individual phases and solid solutions crystallizing in kosnarite and langbeinite structure types were identified; their crystallographic parameters were calculated. The catalytic properties of phosphates Ca_{0.5(1 + x} )Cr _x Ti_{2 ? x} (PO₄)₃ in methanol conversion were studied.     

Electroconduction of Solid Solutions Na3 – 2x M x PO4(M = Cd, Pb)

In the sodium-orthophosphate-based solid solutions in Na_{3 – 2x} M _x PO₄ systems (M = Cd, Pb), the electroconduction is maximum near the upper concentration boundaries of the single-phase regions: x 0.4 for M = Cd and x 0.25 for M = Pb. The conductivity values at 300°C are 6.25 × 10^–3 and 2.5 × 10^–3 S/cm, respectively. The conduction of synthesized solid electrolytes has a co-cation nature. Their electric characteristics, inferior to those of the Na₃PO₄-based solid solutions obtained via heterovalent substitutions of another type, may be a manifestation of an effect similar to the polyalkali effect.     

Electroconductivity of Solid Electrolytes in the Systems K3–2x M x PO4 (M = Ca, Sr, Ba)

Solid electrolytes K_{3 – 2x} M _x PO₄ (M = Ca, Sr, Ba) are synthesized and the temperature and concentration dependences of their electroconductivity are studied. Adding calcium and strontium stabilizes the high-temperature -form of K₃PO₄ at room temperature, while barium-containing solid electrolytes undergo an eutectoid decomposition below 430°C. Maximum electroconductivity is exhibited by K_{3 – 2x} Sr _x PO₄ (7.1 × 10^–3 and 1.25 × 10^–1 S cm^–1 at 300 and 700°C).     

Ca3(P x V1 − x O4)2: Eu3+ nanophosphor synthesis, controlled microstructure, and photoluminescence

In this paper, Eu³⁺-doped Ca₃(P _x V_{1 ? x} O₄)₂ (x = 0.1, 0.4, 0.7) nanophosphors were synthesized in the presence of sodium dodecyl benzene sulfonate (SDBS). The products present interesting and regular morphologies under the mild conditions. For Ca₃(P _x V_{1 ? x} O₄)₂: Eu³⁺, they have the similar phase and their morphologies vary with the content ratio of P to V. Furthermore, the luminescence behavior of Eu³⁺ has been investigated in this one kinds of matrices. In Ca₃(P _x V_{1 ? x} O₄)₂: Eu³⁺, the ⁵ D ₀-⁷ F ₂ emissions of Eu³⁺ were the strongest, indicating that the Eu³⁺ site is without inversion symmetry, the host compositions with different molar ratio of P to V have; great influence on the luminescent performance. Among those products, The value of I ₆₁₅/I ₅₉₃ for Eu³⁺ in Ca₃(P_0.7V_0.3O₄)₂ host lattice is the biggest. The substitution of PO ₄ ^3? for VO ₄ ^3? increase the ratio of surface Eu cations as well as the value of I ₆₁₅/I ₅₉₃ of Eu³⁺.     

Synthesis and electrical properties of variable-composition phases Rb1 − x A1 − x R1 + x (MoO4)3 (0 ≤ x ≤ 0.2; A = Mg, Mn, Co, Ni; R = Sc, Yb, Lu)

Subsolidus region of the ternary systems Rb₂MoO₄-AMoO₄-R₂(MoO₄)₃, in which variable-composition phases Rb_{1 ? x} A_{1 ? x} R_{1 + x} (MoO₄)₃ crystallizing in the monoclinic system (space group C2) are formed, was studied. Their crystallographic parameters were calculated; temperature dependences of the electrical conductivity, dielectric constant, and dielectric loss tangent were analized.     

Electrochemical studies of LiCr x Fe x Mn2?2x O4 in an aqueous electrolyte

In this paper, LiCr _x Fe _x Mn_2−2x O₄ (x = 0, 0.05, 0.1) electrode materials were prepared by sol–gel technique and characterized by X-ray diffraction (XRD) and transmission electron microscopy or high-resolution transmission electron microscopy techniques. XRD results reveal that the Cr–Fe-co-doped LiCr _x Fe _x Mn_2−2x O₄ materials are phase-pure spinels. The electrochemical properties of the LiMn₂O₄, LiCr_0.05Fe_0.05Mn_1.9O₄, and LiCr_0.1Fe_0.1Mn_1.8O₄ electrodes in 5 M LiNO₃ aqueous electrolyte were investigated using cyclic voltammetry, AC impedance, and galvanostatic charge/discharge methods. In the current range of 0.5–2 A g⁻¹, the specific capacity of the LiCr_0.05Fe_0.05Mn_1.9O₄ electrode is close to that of the LiMn₂O₄ electrode, but the specific capacity of the LiCr_0.1Fe_0.1Mn_1.8O₄ electrode is obviously lower than that of the LiMn₂O₄ electrode. When the electrodes are charge/discharge-cycled at the high current rate of 2 A g⁻¹, the LiCr_0.05Fe_0.05Mn_1.9O₄ electrode exhibits an initial specific capacity close to that of the LiMn₂O₄ electrode, but its cycling stability is obviously prior to that of the LiMn₂O₄ electrode.     

Supramolecular compounds of chloroaquacomplexes [Mo3Q4(H2O)9−x Clx](4−x )+ (Q = S, Se; x = 2, 3, 5) with cucurbit[n]urils

The following adducts of cucurbit[6]uril and cucurbit[8]uril with triangular cluster chloroaquacomplexes have been prepared and characterized: {[Mo₃S₄(H₂O)₇Cl₂]₂(CB[₆])}Cl₄·13H₂O (I), (H₃O)₂{[Mo₃Se₄×(H₂O)₆Cl₃](CB[6])}Cl₃·3.5H₂O (II) and (H₃O)₂{[Mo₃S₄(H₂O)₄Cl₅](CB[8])}Cl·14H₂O (III). It is shown that the formation of complementary hydrogen bonds in the systems cucurbit[6]uril/[M₃Q₄(H₂O)_9?x Cl_x]^(4?x)+ (x = 1–3) results in a selective isolation of isomers containing chlorine atom in the trans-position to the capping μ₃-ligand. For large x, a selective inclusion of one or another form into the supramolecular compound is also affected by other factors (a system of hydrogen bonds, S?S and S…Cl interactions between cluster complexes, packing effects etc.).     

Synthesis and Ionic Conductivity of LiZr2(VO4)x(PO4)3 – x

Russian Journal of Electrochemistry - Vanadate phosphates LiZr2(VO4)x(PO4)3 – x are synthesized by the sol-gel technique with subsequent annealing and studied using X-ray diffraction...     

Synthesis and Electrochemical Performance of Spinel LiMn2O4—x（SO4）x Cathode Materials

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｒｅｃｅｎｔｙｅａｒｓ ,ｗｉｔｈｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆａｌｌｓｏｒｔｓｏｆｃｅｌｌｕｌａｒｐｈｏｎｅｓ ,ｃａｍｃｏｒｄｅｒｓ ,ｌａｐｔｏｐｃｏｍｐｕｔｅｒｓ ,ｔｈｅｌｉｔｈｉｕｍ ｉｏｎｓｅｃｏｎｄａｒｙｂａｔｔｅｒｉｅｓｂａｓｅｄｏｎｔｈｅｕｓｅｏｆｌｉｔｈｉ ｕｍ ｍａｎｇａｎｅｓｅ ｏｘｉｄｅＬｉＭｎ2 Ｏ4 1,2 ｈａｖｅａｔｔｒａｃｔｅｄｍｕｃｈａｔ ｔｅｎｔｉｏｎ .ＢｕｔｔｈｅＬｉＭｎ2 Ｏ4 ｃａｔｈｏｄｅｍａｔｅｒｉａｌｈａｓａｄｉｓａｄ ｖａｎｔａｇｅｏｆ…     

Characterization of superparamagnetic Mg x Zn1−x Fe2O4 powders

Structural and magnetic properties of Mg _x Zn_1−x Fe₂O₄ powders have been studied with respect to the application for thermal cancer therapy (magnetic hyperthermia). Mg _x Zn_1−x Fe₂O₄ (x=0.1–0.5) powders with particle sizes between 5 and 8 nm were produced by citrate method. The X-ray diffraction patterns of the samples correspond to a spinel phase. The lattice constant and the volume of the elementary cell increase when x changes from 0.1 to 0.5. The FTIR-spectra ascertain the spinel phase formation. The Mossbauer studies reveal the presence of extremely small particles, which undergo superparamagnetic relaxation at room temperature. The core-shell model has been applied to explain quadruple doublets. The quadruple splitting at “shells” is bigger than those at “cores” whereas the isomer shifts remain close. Magnetic studies confirm the presence of extremely small particles that behave as superparamagnetic ones.      

Solid potassium-conducting electrolytes in the K2 − 2x Ga2 − x V x O4 system

New potassium-conducting solid electrolytes based on potassium monogallate in the K_2?2x Ga_2?x V _x O₄ system are synthesized and studied. It is found that an introduction of V⁵⁺ ions leads to a considerable increase in the KGaO₂ conductivity due to the formation of vacancies in the potassium sublattice. The conductivity for optimal compositions is approximately 10^?3 S cm^?1 at 400°C and above 10^?2 S cm^?1 at 700°C. The results are compared with early obtained data for potassium monogallate dopped with four-charged cations.     

BH_4~-,CH_4,NH_4~ ,AlH_4~-,SiH_4,PH_4~ ,GeH_4的SCF-X_a计算方法研究

本文通过球半径比的优化选择,给出了七个含氢正四面等价电子分子的SCF-X。方法非重叠近似方案的计算结果.就中性分子CH_4,SiH_4及GeH_4而言,总能量和结合能计算值有了显著改进,使SiH_4和GeH_4的成键稳定性得到了合理说明.对离子计算,同时给出了Watson球存在和不存在的计算结果,通过对比,说明自由离子是一种更不稳定的状态,而Watson球确是稳定离子的环境的合理模拟.对离子的结合能也作了讨论,并联系了有关晶体化合物的热稳定性作出了解释.与此同时,还发现优化球半径比与中央原子的电负性存在线性关系,且符合于Virial定理的要求。