Phase equilibria in the Sn–As–Ge and Sn–As–P systems

T–x diagrams of polythermal GeAs–SnAs, GeAs–Sn₄As₃ sections of the Sn–As–Ge system and Sn₄P₃–Sn₄As₃ section of the Sn–As–P system were constructed using the results of X-ray powder diffraction and differential thermal analyses. It was found that the section GeAs–Sn₄As₃ is not quasi-binary due to realization of four-phase peritectic transformation L + SnAs ? GeAs + Sn₄As₃ at the temperature of 834 K. The quasi-binary section GeAs–SnAs represents a phase diagram of the eutectic type with the following coordinates of eutectic reaction: temperature of the eutectic point is 840 K, and composition is 20 mol% GeAs. In the Sn–As–P system, the existence of the solid-solution range indicated as (Sn₄As₃) _x (Sn₄P₃)_1?x  was defined. The polythermal section Sn₄P₃–Sn₄As₃ is not quasi-binary due to the fact that in the composition range with a high content of tin arsenide discussed section intersects the peritectic part of the three-phase volume (L + SnAs + α) of the ternary diagram.     

Experimental investigation and thermodynamic modeling of the Au–Ge–Ni system

Abstract  

Phase equilibria in the Au–Ge–Ni ternary system were studied by means of scanning electron microscopy, electron probe microanalysis, X-ray diffraction, and differential scanning calorimetry. The phase relations in the solid state at 600 °C as well as a vertical section at Au₇₂Ge₂₈–Ni were established. No ternary compound was found at 600 °C. On the basis of the experimental phase equilibria data, a thermodynamic model of the Au–Ge–Ni ternary system was developed using the CALPHAD method. Thermodynamically calculated phase diagrams are shown at 600 °C, in two vertical sections and the liquidus projection. Reasonable agreement between the calculations and the experimental results was achieved.     

Glass transition and crystallization kinetics analysis of Sb–Se–Ge chalcogenide glasses

Differential thermal analysis (DTA) has been employed to investigate the effect of Ge addition on the glass transition behavior and crystallization kinetics of Sb₁₀Se_90?xGe_x (x = 0, 19, 21, 23, 25, 27) alloys. The three characteristic temperatures viz. glass transition (T _g), crystallization (T _c), and melting (T _m) have been determined and found to vary with the heating rates and Ge content. Thermal stability and glass forming tendency have been evaluated in terms of ΔT (= T _c ? T _g) and reduced glass transition temperature. The activation energies for glass transition and crystallization have been used to analyze the nucleation and growth process. The activation energy analysis also determines the suitability of alloys to be used in switching applications. Results have been interpreted in terms of bond energies and structural transformations in the investigated alloys.     

Experimental investigation and thermodynamic prediction of the Al–Ge–Zn phase diagram

The knowledge of the phase diagram of the Al?CGe?CZn ternary system is of importance in the development of high temperature soldering materials. In this study, the phase diagram of the Al?CGe?CZn ternary system was calculated by the calculation of phase diagrams method using binary thermodynamic parameters included in the COST MP0602 thermodynamic database. Chosen alloys with compositions along two vertical sections with molar ratio Al/Ge?=?3/1 and 1/3 were measured using DTA (differential thermal analysis). The experimentally determined phase transition temperatures from this work and phase equilibria data from literature were compared with calculation results and good mutual agreement was noticed.     

Halogen-Substituted Cyclotrigermenes: The π(Ge = Ge)-σ*(Ge–X) Interaction and a Unique Dynamic Behavior

Abstract

The halogen-substituted cyclotrigermenes (^tBu₃Si)₃Ge₃X (X = F, Cl, Br, I) (2) were synthesized by the reaction of tris(tri-tert-butylsilyl)cyclotrigermenylium tetrakis(2,3,5,6-tetrafluorophenyl)borate) (1 ⁺?TTFPB^?) with potassium halides (KF, KCl, KBr, KI). Intramolecular halogen migration over the three-membered ring skeleton was observed in the solution.

GRAPHICAL ABSTRACT     

Crystal structures,site occupations and phase equilibria in the system V–Zr–Ge

The V–Zr–Ge system was studied for two isothermal sections at 900 and 1200 °C. Three ternary compounds VZrGe (tI12, I4/mmm, CeScSi-type), V_xZr_5?xGe₄ (oP36, Pnma, Sm₅Ge₄-type) and V_4+xZr_2?xGe₅ (oI44, Ibam, Si₅V₆-type) were structurally characterized. Optical microscopy and powder X-ray diffraction (XRD) were used for initial sample characterization and electron probe microanalysis (EPMA) of the annealed samples was used to determine the exact phase compositions. The variation of the cell parameters of the various ternary solid solutions with the composition was determined. The three ternary phases were structurally characterized by means of single crystal and powder XRD. While VZrGe is almost a line compound, V_xZr_5?xGe₄ (0.2 ≤ x ≤ 3.0) and V_4+xZr_2?xGe₅ (0.06 ≤ x ≤ 1.2) are forming extended solid solution ranges stabilized by differential fractional site occupancy of V and Zr on the metal sites.     

Study and 3D modeling of the phase diagram of the Ag–Ge–Se system

In view of the contradictoriness of the literature data, phase equilibria in the Ag–Ge–Se system were restudied by differential thermal analysis and X-ray powder diffraction analysis. A number of polythermal sections and an isothermal section at room temperature of the phase diagram were constructed, and so was the projection of the liquidus surface. The primary crystallization fields of phases and the types and coordinates of in- and monovariant equilibria were determined. It was shown that, in the system, a single ternary compound, Ag₈GeSe₆, forms, which undergoes congruent melting at 1175 K and a polymorphic transformation at 321 K. The formation of the compounds Ag₂GeSe₃ and Ag₈GeSe₅, which was previously reported in the literature, was not confirmed. Based on the phase diagrams of boundary binary systems and the results of the differential thermal analysis of a number of samples of the ternary system, equations were obtained for calculation and 3D modeling of the liquidus and phase-separation surfaces.     

Thermodynamic characteristics and phase equilibria in the alloys of the Ge–La system

Mixing enthalpies of melts of the Ge–La system have been measured using isoperibolic calorimetry within two concentration ranges. For the first range (0 < x _La < 0.16 at 1520 K and 0.16 < x _La < 0.29 at 1570 K), agreement with the known literature data is observed within the experimental error. The second range (0.78 < x _La < 1 at 1470 K and 0.7 < x _La < 0.78 at 1580 K) has been studied for the first time. The melts are characterized by very strong exothermal effects of mixing, which have almost symmetrical concentration dependence: ΔH? _La ^∞ = ΔH? _Ge ^∞ = ?245 kJ/mol at 1470 K. A thermodynamic optimization of the activities of the components and the phase diagram of the system have been conducted based on the obtained experimental data, using an ideal associated solution (IAS) model.     

Calorimetric study of Sb-modified Ge–Se–Te glassy alloys

The glassy compositions of Ge ₁₆ Se ₅₂ Te _32?x Sb _x system, obtained using rapid melt quenching technique, have been characterized by calorimetric study at different heating rates in this study. A systematic investigation of the crystallization kinetics is carried out for these compositions. Composition corresponding to atomic % 8 of Sb has good thermal stability. The material exhibits the unique thermal properties, which makes it suitable to use for electrical or memory switching devices. Various thermal parameters, activation energies of glass transition and crystallization are calculated using relevant approaches.     

Reactivity of the Ge–H,Sn–H,P–H,and Se–H Bonds in Radical Abstraction Reactions

The experimental data for the liquid- and gas-phase reactions of atoms and radicals with organoelement compounds R _{n – 1}E–H

Atomistic simulation of Si–Ge clathrate alloys

The structural, elastic, vibrational and thermodynamic properties of Si–Ge clathrate alloys have been investigated by lattice dynamics (LD) and molecular dynamics (MD) calculations based on the Tersoff’s potential. The structural properties, static cohesive energies and bulk moduli determined from the LD simulations agree with the results of the first-principles approach in the literature. In addition, we estimated the Debye temperatures from the calculated elastic constants. They demonstrate a decay trend as the Ge composition increases. The vibrational properties, especially the phonon density of states, were investigated in comparison with those of the ordinary Si–Ge diamond-like alloys. The MD calculations were then carried out for the clathrate alloys above their respective Debye temperatures to obtain the pair correlation functions and the internal energies.     

Ge–Ge Bond-Forming Reactions from Bis(germyl)palladium Complexes with Chelating Diphosphine Ligands

Abstract

Ge–Ge bond-forming reactions of bis(germyl)palladium complexes with chelating diphosphine ligands have been investigated. Addition of excess dmpe (1,2-bis(dimethylphosphino)ethane) to the solution of Pt(GeHPh₂)₂(dmpe) (1) gave a mixture of oligogermanes in low yields, while a similar reaction of depe (1,2-bis(diethylphosphino)ethane) with Pt(GeHPh₂)₂(depe) (2) afforded H(GePh₂)₂H selectively in 93% NMR yield.

GRAPHICAL ABSTRACT     

Synthesis and characterization of Nb–Ge doped titanosilicate nanoparticles and study of their selectivity for absorption of 137Cs and 90Sr

In this research, for the first time Nb and Ge were doped into titanosilicate nanoparticles up to 25% simultaneously. Crystalline phases and morphology of the synthesized samples were studied by X-ray diffraction (XRD) method and scanning electron microscope (SEM), respectively. Elemental analysis of the samples was performed using X-ray fluorescence (XRF) and Energy dispersive X-ray (EDX) techniques. Surface area of the samples was measured by BET method. Ion exchange potential of the synthesized samples for Sr²⁺ and Cs⁺ and effective parameters such as concentration, temperature, time, and pH were investigated. In addition,¹³⁷Cs and ⁹⁰Sr radio nuclides absorption in the best appropriate sample was examined. The selectivity of the samples for absorption of ¹³⁷Cs and ⁹⁰Sr was studied by gamma spectroscopy, liquid scintillation spectrometry, and atomic absorption spectroscopy methods. The obtained results showed that the prepared samples had good potential for absorption of ¹³⁷Cs and ⁹⁰Sr from the model solution. The sample containing equal amount of niobium and germanium, removed completely the ¹³⁷Cs within the waste water of Tehran nuclear reactor and ⁹⁰Sr in the desired solution.     

Isomeric pyridylcarbenes and their Si and Ge heavier analogues at DFT: stabilization through π–p or n–p interaction

To realize the effects of the pyridyl group on the stability, multiplicity, and geometry of isomeric pyridylcarbenes and their heavier Si and Ge analogues, a theoretical study was performed at B3LYP/6-311++G(d,p)//B3LYP/6-31G(d). The behavior of nitrogen atom was totally different in each multiplicity (singlet and triplet), structural isomer (ortho-, meta-, and para-), and divalent center (C, Si, and Ge). All pyridylcarbenes have triplet ground states, while the stable silylene and germylene analogues are singlet. The pyridyl group stabilizes both singlet and triplet states divalent centers with more pronounced effects on the singlet states in the order: carbene>germylene>silylene. While all planar species benefit from common π–p conjugative interaction of the pyridyl ring, in the ortho-isomers of 2-pyridylsilylene and 2-pyridylgermylene there is another interaction, n–p, that leads to two stable non-planar conformers. This finding is confirmed by NBO charges, calculated UV–vis spectra, philicity indices (N and ω), and isodesmic reactions.     

Formation of short-range order in Al–Ge–Fe melts: influence of composition

ABSTRACT

The short-range order in Al–Ge–Fe melts has been studied by X-ray diffraction and reverse Monte Carlo simulations in wide concentration range. Influence of the replacement of one component by another while the content of third component is constant on the formation of a local structure of ternary melts has been discussed. It has been shown that at Ge content less than 30 аt. % Ge atoms are uniformly distributed in the volume of the Al–Ge–Fe melts and atomic clusters with structure similar to the liquid germanium are formed at content more than 30 аt. % Ge. The addition of the third component (Ge or Al) to the binary Al–Fe or Fe–Ge melts, correspondingly, results in competition between Al and Ge atoms in formation of the local structure around Fe atoms. The obtained concentration dependences of the nearest neighbour distances point out that the ternary interactions take place in the Al–Fe–Ge melts.     

Ab initio study of mechanism of cycloaddition reaction between H2Ge = Ge: and acetone

The mechanism of the cycloaddition reaction between singlet H₂Ge = Ge: and acetone has been investigated with CCSD(T)//MP2/6-31G* method. From the potential energy profile, it could be predicted that the reaction has two competitive dominant reaction pathways. The reaction rule presented is that the two reactants firstly form a four-membered Ge-heterocyclic ring germylene through the [2 + 2] cycloaddition reaction. Because of the 4p-unoccupied orbital of Ge atom in the four-membered Ge-heterocyclic ring germylene and the π-orbital of acetone forming a π → p donor–acceptor bond, the four-membered Ge-heterocyclic ring germylene further combines with acetone to form an intermediate. Because the Ge atom in intermediate happens sp³ hybridization after transition state, then, intermediate isomerizes to a spiro-Ge-heterocyclic ring compound via a transition state. Simultaneously, the ring strain of the four-membered Ge-heterocyclic ring germylene makes it isomerize to a twisted four-membered ring product.