Ab initio properties of MgAlk (Alk = Li, Na, K, Rb, Cs)

High level ab initio calculations are performed on the ground electronic state of diatomic molecules MgAlk (Alk = Li, Na, K, Rb, Cs). Potential energy curves and dipole moment functions are determined making use of the single-reference unrestricted and restricted coupled-cluster methods with large basis sets. Basic spectroscopic properties of the ground electronic states are derived from ro-vibrational bound state calculations.     

Thermodynamics of dehydration of MAsUO6·xH2O (M = Li,Na, K,Rb, Cs) Crystal Hydrates

The existence regions of crystal hydrates in the systems MAsUO₆-H₂O (M = Li, Na, K, Rb, Cs) in the coordinates water vapor pressure-temperature were studied by the isopiestic method and static tensimetry. All individual compounds formed in these systems were isolated and studied by reaction calorimetry. The enthalpies of their formation and dehydration were determined.     

Photocatalytic properties and hydration of perovskite-type layered titanates A2Ln2Ti3O10 (A = Li, Na, K; Ln = La, Nd)

Layered perovskite-type oxides A₂Ln₂Ti₃O₁₀ (A = Li, Na, K; Ln = La, Nd) prepared by solid-phase synthesis and their hydrated forms were characterized by the methods of TGA, XRD, and by UV-Vis spectroscopy. Photocatalytic activity of A₂Ln₂Ti₃O₁₀ oxides in reaction of hydrogen evolution from aqueous alcoholic suspensions irradiated by UV-light was studied. It was shown that the ability to intercalation of water into interlayer space essentially affects the rate of photoinduced hydrogen evolution and is a determining factor leading to a high photocatalytic activity.     

Phase formation in the Re-Se-Br-MBr systems (M = Li, Na, K, Rb, Cs)

Phase formation in the Re-Se-Br-MBr systems (M = K, Rb, Cs) was studied by NMR spectroscopy and powder X-ray diffraction. The reactions taking place in alkali metal halide melts were found to give, among the series of cluster anions [{Re₆Se_{8 − n} Br _n }Br₆]^{(4 − n)}− (0 ≤ n≤ 4), polymeric complexes Re₆Se₈Br ₂ and M₂Re₆Se₈Br₄ (M = Cs, Rb) and salts containing cluster anions [Re₆Se₆Br₈]²⁻ and [Re₆Se₇Br₇]³⁻ as the major products. The effect of the alkali metal cation on the product composition and ratio was established. Original Russian Text ? S.S. Yarovoi, Yu.V. Mironov, S.V. Tkachev, V.E. Fyodorov, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 2, pp. 344–349.     

Photocatalytic property and electronic structure of triple-layered perovskite tantalates, MCa2Ta3O10 (M = Cs, Na, H, and C6H13NH3)

The Dion-Jacobson series of triple-layered perovskite tantalates (MCa2Ta3O10, M = Cs, Na, H, and C6H13NH3) were synthesized to evaluate their photocatalytic activity for overall water splitting to evolve H2/O2 under UV irradiation. The photocatalytic activity was susceptible to the hydration of interlayer space. The hydrous Na phase exhibited much higher activity (H2: 308 micromol.h(-1)) compared to the anhydrous Cs phase (24 micromol.h(-1)) and the hydrous H phase (22 micromol.h(-1)) in the presence of 0.5 wt % Ni impregnated. H2O/D2O isotopic experiment suggested that the hydrated interlayer plays as an active site for water splitting, where the high mobility of water molecule in the interlayer should correlate with the total photocatalytic activity. The FLAPW electronic structure calculation demonstrated that the terminating oxygen site, O4, which faces to the interlayer space, contributes largely to the top of the valence band. Judging from comparison with the double-layered tantalates, MLaTa2O7, in our previous study, the contribution of terminating oxygen site to the band structure is supposed to depend on the number of perovskite layers.     

A study of the thermal decomposition of layered perovskite-like oxides ANdTiO4 and A2Nd2Ti3O10 (A = Na,K)

The thermal stability of cation-ordered perovskite-like layered titanates ANdTiO₄ and A₂Nd₂Ti₃O₁₀ (A = Na, K) is studied in the temperature range of 900–1400°C. The structural chemical mechanism of their thermal decomposition is established. A comparative analysis of the thermal stability of compounds with different thicknesses of the perovskite layer and different nature of the alkali cation is performed. The observed thermal behavior is explained from crystal chemical standpoints.     

Interrelation between the physicochemical properties of MnCl2-MCl (M = Li, Na, K, Rb, and Cs) melts

Our own experimental studies of vapor pressure and surface tension were used to analyze isotherms of various types of the properties under consideration. The data obtained were processed using a mathematical model to calculate the molar surface and excess molar Gibbs energy, which clearly indicated that the surface properties obeyed the general rules that governed changes in these properties of solutions according to the position of alkali metals in the periodic table of the elements. The data on various physicochemical properties of the cesium chloride-manganese chloride system are evidence of the presence of singular extremum points on concentration dependence isotherms.     

Thermochemistry of Li, Na, K, Rb and Cs alkylated phenoxides

Lattice energies and thermochemical radii of the anions OR⁻ (R = 2-Me; 2,6-Me₂; 2,4,6-Me₃; 2,6-t-Bu₂) in alkali metal phenoxides, MOR (M = Li, Na, K, Rb and Cs) were investigated based on the corresponding standard molar enthalpies of formation determined by reaction-solution calorimetry. The results obtained at 298.15 K were as follows: (MOR, cr)/kJ mol⁻¹ = −398.4 ± 1.1 (LiO-2-MePh), −423.4 ± 1.6 (LiO-2,6-Me₂Ph), −457.3 ± 7.1 (LiO-2,4,6-Me₃Ph), −346.6 ± 1.4 (NaO-2-MePh), −399.1 ± 1.5 (NaO-2,6-Me₂Ph), −422.4 ± 7.1 (NaO-2,4,6-Me₃Ph), −496.6 ± 7.1(NaO-2,6-t-Bu₂Ph), −367.8 ± 1.2 (KO-2-MePh), −399.1 ± 1.4 (KO-2,6-Me₂Ph), −368.8 ± 1.2 (RbO-2-MePh), −403.6 ± 1.3 (RbO-2,6-Me₂Ph), −387.0 ± 1.6 (CsO-2-MePh) and −413.6 ± 1.3 (CsO-2,6-Me₂Ph). Estimates of thermochemical raddi, lattice energies and standard enthalpies of formation of not experimentally measured alkali metal phenoxides was successfully done with a model based on the Kapustinskii equation and the set of values experimentally determined.     

Über Hexafluoroindate(III): A2TllnF6 (A=Rb,Cs), (RbTI)BlnF6 (B= Na,Ag, K) und A2AglnF6 (A=Rb,TI,Cs)

On Hexafluoroindates(II1): A₂TlInF₆ (A = Rb, Cs), (RbTI)BInF₆ (B = Na, Ag, K), and A₂AgInF₆ (A = Rb, TI, Cs) By heating the binary components in a closed system are new prepared the compounds Rb₂AgInF₆, Rb₂CsInF₆, (RbTl)NaInF₆ (RbTI)AgInF₆, (RbTI)KInF₆, Tl₂AgInF₆, Cs₂AgInF₆ and Cs₂TlInF₆, all cubic, colourless Elpasolithes, as well as Rb₂TlInF₆, according to powder photographs tetragonal. The Madelung Part of Lattice Energy, MAPLE, is calculated and discussed.     

Electronic structure and properties of isoelectronic magic clusters: Al13X (X=H,Au,Li,Na,K,Rb,Cs)

The equilibrium structure, stability, and electronic properties of the Al(13)X (X=H,Au,Li,Na,K,Rb,Cs) clusters have been studied using a combination of photoelectron spectroscopy experiment and density functional theory. All these clusters constitute 40 electron systems with 39 electrons contributed by the 13 Al atoms and 1 electron contributed by each of the X (X=H,Au,Li,Na,K,Rb,Cs) atom. A systematic study allows us to investigate whether all electrons contributed by the X atoms are alike and whether the structure, stability, and properties of all the magic clusters are similar. Furthermore, quantitative agreement between the calculated and the measured electron affinities and vertical detachment energies enable us to identify the ground state geometries of these clusters both in neutral and anionic configurations.     

Mixed Alkali Neodymium Orthoborates: K9Li3Nd3(BO3)7 and A2LiNd(BO3)2 (A = Rb,Cs)

Crystals of mixed alkali neodymium orthoborates, K₉Li₃Nd₃(BO₃)₇ and A₂LiNd(BO₃)₂ (A = Rb, Cs) were obtained by spontaneous crystallization. K₉Li₃Nd₃(BO₃)₇ crystallizes in space group P2/c with cell parameters of a = 11.4524(7) Å, b = 10.1266(6) Å, c = 12.3116 (10) Å, β = 122.0090(10)°. In the structure, NdO₈ polyhedra share corners and connect with planer BO₃ groups to form infinite [Nd₃B₃O₂₁]_n chains. These chains are linked by additional BO₃ groups to produce a double layer of [Nd₆B₆O₃₈]_n blocks in the ac plane with K and Li ions filled into the cavities. A₂LiNd(BO₃)₂ (A = Rb, Cs) crystallizes in space group Pbcm, with cell parameters of a = 7.113(2) Å, b = 9.691(3) Å and c = 10.135(3) Å for Rb₂LiNd(BO₃)₂, and a = 7.2113(3) Å, b = 9.9621(4) Å, and c = 10.3347(4) Å for Cs₂LiNd(BO₃)₂. In the structure, NdO₈ polyhedra are corner‐sharing with each other and further interlinked by BO₃ groups to comprise the infinite [Nd₄B₄O₂₄] sheets in the bc plane, with Rb/Cs and Li ions occupying the interlayered space. The compounds show effective near‐IR emission and their associated lifetimes are obtained by fluorescence spectra.     

Enhanced water splitting activity of M-doped Ta(3)N(5) (M = Na, K, Rb, Cs)

We use a highly aligned Ta(2)O(5) nanochannel structure to fabricate alkali metal ion (Na, K, Rb or Cs) doped Ta(3)N(5)via solution seeding and thermal conversion in NH(3). Under optimized conditions the resulting doped structures show a strongly enhanced visible light water splitting performance in comparison to undoped Ta(3)N(5).     

MZr2（AsO4）3（M=Na,K,Rb,Cs）的水热合成与结构表征

用水热晶化法合成了MZr_2(ASO_4)_3(M=Na,K,Rb,Cs)系列化合物。研究了反应物浓度、配比及不同砷源等水热晶化条件对产物物相的影响。用XRD、IR和Raman光谱对产物进行了表征。4种晶体的振动光谱由钠到铯呈现出规律性变化。     

Control of structures and sorption properties of ionic crystals of A2[Cr3O(OOCC2H5)6(H2O)3]2[alpha-SiW12O40] (A = Na, K, Rb, NH4, Cs, TMA)

The complexation of Keggin-type polyoxometalate [alpha-SiW 12O 40] (4-), macrocation [Cr 3O(OOCC 2H 5) 6(H 2O) 3] (+), and monovalent cation A (+) forms ionic crystals of A 2[Cr 3O(OOCC 2H 5) 6(H 2O) 3] 2[alpha-SiW 12O 40]. nH 2O [A = Na ( 1a), K ( 2a), Rb ( 3a), NH 4 ( 4a), Cs ( 5a), and tetramethylammonium (TMA) ( 6a)]. Single crystal (1a- 4a and 6a) and powder (5a) X-ray analyses have shown that the ionic crystals possess 2D layers of polyoxometalates and macrocations. Compounds 2a- 5a had almost the same structure, while the layers in 1a and 6a stack in different ways. The structures and sorption properties of 2b- 5b are investigated in more detail. The interlayer distances of guest free phases 2b- 5b increase with the increase in the ionic radii of the monovalent cations, which reside between the layers. Compounds 2b- 5b possess hydrophobic and hydrophilic channels, which exist between the layers and through the layers, respectively. The volumes of the hydrophobic channels increase in the order of 2b < 3b approximately 4b < 5b, and those of the hydrophilic channels increase in the order of 2b < or = 3b < or = 4b < 5b. Single-crystal X-ray structure analyses of 2a- 4a have shown that the water of crystallization resides in the hydrophilic channel. It is probable that the water of crystallization in 5a resides in the hydrophilic channel in the same manner as those in 2a- 4a since 2a- 5a have almost the same structure. The water vapor sorption profiles of 2b- 5b are approximately reproduced by a linear driving force model. Therefore, water molecules sorbed in 2b- 5b probably reside in the hydrophilic channel. The n-propanol sorption profiles are reproduced by the summation of the linear driving force model, showing that two independent barriers exist in the n-propanol sorption. The in situ IR spectra of n-propanol sorbed showed the presence of two n-propanol species. These data show that n-propanol is sorbed into both hydrophilic and hydrophobic channels. Compound 5b sorbs halocarbons in the hydrophobic channel, while 2b- 4b exclude them.     

CH_2=CH(XM)(X=S,Se,Te;M=H,Li,Na,K,Rb,Cs,-)的从头算研究

应用相对论有效势在ＭＰ２水平上对ＣＨ２ＣＨ（ＸＭ）（Ｘ＝Ｓ，Ｓｅ，Ｔｅ；Ｍ＝Ｈ，Ｌｉ，Ｎａ，Ｋ，Ｒｂ，Ｃｓ，－）进行了从头计算研究．结果表明，所研究的化合物都有平面式和非平面桥式两种构型．分析了碱金属离子对两可亲核底物ＣＨ２ＣＨＸ－（Ｘ＝Ｓ，Ｓｅ，Ｔｅ）离域化的影响，并用自然布局分析方法（ＮＰＡ）研究了电荷分布的变化，得出了有价值的结论．     

Structural phase stability studies on MBeH3 (M = Li, Na, K, Rb, Cs) from density functional calculations

Density functional theory calculations within the generalized-gradient approximation are used to establish the ground-state structure, equilibrium structural parameters, and electronic structure for MBeH(3) phases. From the 24 structural arrangements used as inputs for structural optimization calculations, the ground-state crystal structures of MBeH(3) phases have been predicted. At ambient conditions, LiBeH(3) and NaBeH(3) crystallize with perovskite-related orthorhombic and cubic structures, respectively. The remaining phases KBeH(3), RbBeH(3), and CsBeH(3) crystalize in a monoclinic structure. In the predicted phases one can store up to 15.93 wt % of hydrogen. The formation energy for the MBeH(3) phases have been investigated along different reaction pathways. The electronic structures reveal that all these phases are insulators with estimated band gaps varying between 1.79 and 3.44 eV.     

298.15和308.15 K时1,2-丙二醇+MCl (M=Na,K, Rb,Cs)+H2O三元体系的溶解度、密度和折光率

系统研究了1,2-丙二醇+MCl (M=Na, K, Rb, Cs)+H₂O三元体系在298.15 和308.15 K时的等温相平衡. 采用硝酸汞滴定法测定了体系中无机盐的含量, 采用安东帕RXA170 折光率仪及DMA4500 密度计测定了所有体系的折光率和密度数值. 报道了1,2-丙二醇质量分数从0增加到0.9过程中饱和及不饱和三元溶液体系的等温溶解度、密度和折光率数据. 实验结果发现, 随着1,2-丙二醇的不断加入, 饱和溶液的溶解度和密度均呈现出减小的趋势, 而折光率的变化则呈现出相反的趋势. 采用经验方程关联了不同醇水比条件下不饱和溶液的密度和折光率实验数据, 获得了较为理想的拟合结果. 本研究的开展充实了碱金属盐在混合溶剂中的热力学数据, 为相关溶液化学研究奠定了基础.