Ge Compounds Research Articles

Half-metallic and thermodynamic properties of new d 0 CsCaZ (Z= Ge, Sn and Pb) half Heusler alloys: A spin-based devices vision for the future

Density functional theory (DFT) was applied to investigate the structural, electronic, elastic, magnetic, thermodynamic and half-metallic properties of the newly d0 Heusler alloys (HAs) CsCaZ (Z= Ge, Sn and Pb). Spin-polarised calculations show that the compounds studied are half-metallic with a magnetic moment of 1.00 μB at the equilibrium lattice parameter, which obeys the well-known Slater–Pauling rule Mtot = 8 – Zt. The half-metallic behavior of the compounds CsCaGe, CsCaSn and CsCaPb is predicted with respect to the equilibrium lattice constants for CsCaGe, CsCaSn and CsCaPb with a narrow band gap in the majority spin channel. Furthermore, the elastic constants (Cij) showed that these materials are ductile and anisotropic. In addition, the negative values of the calculated formation energy and cohesion energy indicate that CsCaZ (Z= Ge, Sn and Pb) are likely to be experimentally synthesized. Non-equilibrium Gibbs function is employed to calculate the thermodynamic properties through the quasi-harmonic Debye model in which the bulk modulus, heat capacity, Debye temperature, thermal expansion coefficient, and entropy are investigated at 0-20 Gpa pressure and 0-1200 K temperature ranges. The significant half-metallic behavior makes the CsCaZ (Z= Ge, Sn and Pb) compounds strong candidates for spintronic applications.

GGA and GGA + U Study of ThMn2Si2 and ThMn2Ge2 Compounds in a Body-Centered Tetragonal Ferromagnetic Phase.

Our study used the full-potential linearized augmented plane waves (FP-LAPW) method to conduct a first-principles evaluation of the structural, electronic, and magnetic properties of ThMn2X2 (X = Si and Ge) compounds. To establish theoretical dependability with the currently available experimental results, computations for the structural findings of ternary intermetallic thorium (Th)-based compounds were achieved using the generalized gradient approximation in the scheme of Perdew–Burke–Ernzerhof (PBE–GGA) potential, while the generalized gradient approximation plus the Hubbard U (GGA + U) approach was employed to improve the electrical and magnetic properties. In contrast with both the paramagnetic (PM) and antiferromagnetic (AFM) phases, the ThMn2X2 compounds were optimized in a stable ferromagnetic (FM) phase, which was more suited for studying and analyzing magnetic properties. The electronic band structures (BS) and the density of state (DOS) were computed using the two PBE–GGA and GGA + U approximations. The thorium (Th)-based ThMn2X2 compound has full metallic character, due to the crossing and overlapping of bands across the Fermi level of energy, as well as the absence of a gap through both spin (up and down) channels. There was a significant hybridization between (Mn-d and (X = Si and Ge)-p states of conduction band with Th-f states in the valence band. The total magnetic moment of ThMn2Si2 in the ferromagnetic phase was 7.94534 μB, while for ThMn2Ge2 it was 8.73824 μB with a major contribution from the Mn atom. In addition, the ThMn2Ge2 compound’s total magnetic moment confirmed that it exhibits higher ferromagnetism than does the ThMn2Si2 compound.

Heavy thallium based fluoroperovskite TlAF3 (A = Ge, Sn and Pb) compounds: a computational investigation

The use of heavy elements to build a stable system increases the effective atomic number, making it useful in a variety of applications such as radiation detection and shielding. This study reports the density functional theory (DFT) based investigations on new Thallium based heavy fluoroperovskites TlAF3 (A = Ge, Sn and Pb). These compounds have a cubic perovskite structure with optimal lattice constants ranging from 4.49 to 4.85 Å. Electronic behaviors of the compounds is found to be insulating with the maximum band gap of up to 1.90 eV, having indirect band nature. In all investigated compounds, the fluorine atom provides a significant number of electronic states to the valence and conduction bands. The optical activity is evaluated by determining the refractive index, extinction coefficient, optical conductivity, reflectivity, and absorption coefficients up to photon energies of 20 eV. The properties of present compounds are being reported for the first time.

Movable triple points and Dirac points in centrosymmetric AB2 (A = Cr, Mo; B = Si, Ge) compounds.

Topological semimetals with nontrivial band crossing points have attracted widespread interest in recent years. Here, we propose that AB2 (A = Cr, Mo; B = Si, Ge) compounds are topological semimetals that feature a pair of triple points (TPs) on high-symmetry paths in the absence of spin-orbital coupling (SOC). In particular, the existence of this kind of TP is accompanied by a quadratic nodal line (QNL). In addition, we discover that these TPs are movable. Under a triaxial strain, we can change their positions on high-symmetry paths. When considering SOC, TPs transform into two pairs of type-II Dirac points along the high-symmetry path. Akin to TPs without SOC, each pair of Dirac points can also shift their positions on the high-symmetry paths under a triaxial strain. To characterize this property of TPs and Dirac points, we construct an effective model around the TPs and Dirac points, finding that there indeed exists a parameter that could characterize the movable properties for the TPs and Dirac points. According to the bulk-surface correspondence, we also discover that the length of the Fermi arcs that correspond to the nontrivial band crossings are also altered when changing their positions. Meanwhile, the shapes of Fermi arcs are also changed. Therefore, our work provides a platform to study the band crossings that are movable. The controllable fermions are beneficial to utilize the topological materials in nano-devices.

Influence of Main Group Elements on Structural, Electronic, Magnetic and Half-Metallic Properties of Do3-Type Mn3z (Z = Al, Ga, in, Si, Ge, Sn, P, as and Sb) Compounds - a Dft Study

Influence of Main Group Elements on Structural, Electronic, Magnetic and Half-Metallic Properties of Do3-Type Mn3z (Z = Al, Ga, in, Si, Ge, Sn, P, as and Sb) Compounds - a Dft Study

Computational investigation of structural, magnetic, elastic, and electronic properties of Half-Heusler ScVX (X = Si, Ge, Sn, and Pb) compounds

Computational investigation of structural, magnetic, elastic, and electronic properties of Half-Heusler ScVX (X = Si, Ge, Sn, and Pb) compounds

Main Group Catalysis: Cationic Si(II) and Ge(II) Compounds as Catalysts in Organosilicon Chemistry

Cyclopentadienyl (Cp)-coordinated cationic Si(II) (1) and Ge(II) compounds (2) are a new class of catalysts for various transformations in organosilicon chemistry. This review demonstrates that these compounds effectively catalyze technically important reactions, such as the hydrosilylation of carbon-carbon multiple bonds and various types of siloxane-coupling reactions, e.g., the Piers-Rubinsztajn reaction and the oxidative siloxane coupling reaction. Whereas the cationic Si(II) compounds are sensitive to air and moisture, the corresponding cationic Ge(II) compounds are bench stable, thus offering further advantages. The new catalysts contribute to the growing need for the substitution of transition metals and heavier main group metals by their lighter congeners, especially in industrially relevant organosilicon chemistry.

Theoretical investigation of ternary semiconductors half-Heusler RhTaZ (Z = Si, Ge and Sn) for thermoelectric applications

The structural, electronic, elastic, thermodynamic and thermoelectric properties of RhTaZ (Z = Si, Ge and Sn) half-Heusler materials have been studied using density functional theory. We have found that the compounds studied can be experimentally synthesized. Also, RhTaZ (Z = Si, Ge and Sn) alloys exhibit a semiconductor behavior following the Slater–Pauling rule. The elastic properties calculated confirm that our compounds are mechanically stable. Using Debye’s quasi-harmonic model, the thermodynamic properties of these half-Heusler alloys were investigated. For the study of thermoelectric properties, the semi-classical Boltzmann theory, as implemented in the BoltzTraP code, has been used. The high values obtained from the figure of merit for RhTaZ (Z = Si, Ge and Sn) compounds suggest that they are promising candidates for thermoelectric applications at low and high temperatures.

Access to a Variety of Ge(II) and Sn(II) Compounds through Substitution of Hypersilyl Moiety

Access to a Variety of Ge(II) and Sn(II) Compounds through Substitution of Hypersilyl Moiety

Band parameters and thermoelectric properties of chalcopyrite ternary compounds CdXP2 (X = Si, Ge and Sn)

In the present paper, the results of a detailed computational study of the structural, electronic, optical, magnetic and thermoelectric properties of the CdXP2 (X = Si, Ge and Sn) compounds have been studied using the full-potential linearized augmented plane wave (FP-LAPW) method. The calculated structural parameters of the title compounds are in excellent agreement with the available theoretical data. Furthermore, in order to clarify the mechanism of electronic band structure and optical transitions of CdXP2 (X = Si, Ge and Sn), the electronic structure and density of states, complex dielectric function, refractive index with extinction coefficient, optical conductivity and absorption coefficient are calculated for radiations up to 20 eV. Finally, the thermoelectric parameters are computed for 300–900 K temperature range to explore the potential of these compounds for applications in technological devices.

Effects of exogenous germanium and effective microorganisms on germanium accumulation and nutritional qualities of garlic (Allium sativum L.)

Organic germanium (Ge) compounds show vital beneficial effects for our health and are widely used as medical applications and dietary supplements. Inorganic Ge can be absorbed by plants and further accumulated and transformed into organic Ge compounds in plant tissues, which can be further consumed as Ge-rich foods. Meantime, the presence of Ge can improve the physiological functions of plants such as the salt tolerance and the peroxidase activities in leaves. Therefore, improving the Ge content of Ge-rich plants by fertilizing exogenous inorganic Ge is of important and an efficient way to obtain more organic germanium. Garlic is one of the natural Ge-rich plants and possesses prodigious medicinal and nutraceutical properties. The main edible parts of garlic include bulb, scape and seedling in China. However, the effects of exogenous Ge on the Ge accumulation and nutritional qualities of garlic are not apparent, and the suitable applying concentrations and frequencies are also poorly known. Here, using garlic cultivar G024 and GeO2 as exogenous Ge, two experiments were performed to reveal the effects of exogenous Ge on garlic. Besides, a third experiment that brings in the factor of effective microorganisms (EM) inoculation was also conducted to evaluate the combined effects of exogenous Ge and EM application on garlic seedlings. Results showed that foliar spraying 6–72 mg/L GeO2 solutions significantly affects the Ge accumulation and distribution in garlic plants; foliar spraying 9–12 mg/L GeO2 at the bolting period is appropriate for producing the Ge-rich garlic scapes and bulbs; soil supplying 100 mg GeO2 together with EM inoculation are suitable for obtaining Ge-rich garlic seedlings. The present study provided useful information for the field production of Ge-rich garlic.

Orlen lets contract for Lithuanian refinery

Organic germanium (Ge) compounds show vital beneficial effects for our health and are widely used as medical applications and dietary supplements. Inorganic Ge can be absorbed by plants and further accumulated and transformed into organic Ge compounds in plant tissues, which can be further consumed as Ge-rich foods. Meantime, the presence of Ge can improve the physiological functions of plants such as the salt tolerance and the peroxidase activities in leaves. Therefore, improving the Ge content of Ge-rich plants by fertilizing exogenous inorganic Ge is of important and an efficient way to obtain more organic germanium. Garlic is one of the natural Ge-rich plants and possesses prodigious medicinal and nutraceutical properties. The main edible parts of garlic include bulb, scape and seedling in China. However, the effects of exogenous Ge on the Ge accumulation and nutritional qualities of garlic are not apparent, and the suitable applying concentrations and frequencies are also poorly known. Here, using garlic cultivar G024 and GeO2 as exogenous Ge, two experiments were performed to reveal the effects of exogenous Ge on garlic. Besides, a third experiment that brings in the factor of effective microorganisms (EM) inoculation was also conducted to evaluate the combined effects of exogenous Ge and EM application on garlic seedlings. Results showed that foliar spraying 6–72 mg/L GeO2 solutions significantly affects the Ge accumulation and distribution in garlic plants; foliar spraying 9–12 mg/L GeO2 at the bolting period is appropriate for producing the Ge-rich garlic scapes and bulbs; soil supplying 100 mg GeO2 together with EM inoculation are suitable for obtaining Ge-rich garlic seedlings. The present study provided useful information for the field production of Ge-rich garlic.

The structural, electronic and thermodynamic properties of LaRuX (X = Si, Ge) compounds

The structural, electronic and thermodynamic properties of LaRuX (X = Si, Ge) compounds are investigated using density functional theory by the Wien2k code. Using the first-principles procedure, the Hubbard parameter of La 5d electrons and Ru 4d electrons of LaRuX (X = Si, Ge) compounds is calculated. In these calculations, the exchange–correlation potential is calculated using the generalized gradient approximation (GGA) and generalized gradient approximation plus Hubbard parameter (GGA + U). The calculated results indicate that LaRuX (X = Si, Ge) compounds are stable in the nonmagnetic phase. The electron density of states and band structure of LaRuX (X = Si, Ge) compounds within GGA and GGA + U approaches in the presence of spin orbit coupling are calculated. The obtained results of the electronic band structure show that LaRuX (X = Si, Ge) compounds have metallic behavior. Furthermore, thermodynamic properties of LaRuX (X = Si, Ge) compounds using the quasi-harmonic Debye model within GGA and GGA + U approaches are investigated.

Heavier Tetrylenes as Single Site Catalysts

An overview of the development of compounds with heavier low-valent group 14 elements (known as tetrylenes) as single component catalyst for organic transformation has been provided. Compounds with heavier group 14 elements possess stereochemically active lone pairs and energetically accessible π-antibonding orbitals, thereby resembling the electronic configuration of transition-metal compounds. Such compounds with low-valent group 14 elements has been known for small molecule activation since Power's report of dihydrogen activation by a digermyne, but their utilization in catalysis remained as a "Holy Grail" in main group chemistry. In recent years, numerous methodologies have been discovered epitomizing the use of Si(II), Ge(II) and Sn(II) compounds as single site catalysts for hydroboration of aldehydes, ketones, pyridines, cyanosilylation of aldehydes and ketones, N-formylations aromatic amines, dehydrocoupling reactions. This mini-review highlights these significant developments with an emphasis on the mechanistic investigation.

Ruthenium-based half Heusler alloys RuTiX (X = Si, Ge, Sn): An FP-LAPW-based analytical study of structural, electronic, elastic, mechanical and transport properties

An full potential linearized augmented plane wave (FP-LAPW)-based analytical study of structural, electronic, mechanical and thermoelectric properties has been done for the Ruthenium-based half heusler RuTiX (X = Si, Ge and Sn) compounds. An efficient method to develop Half Heusler (HH) alloys is by examining their stability of structure in various phases, by plotting electronic band structures, computing elastic constants and also by studying the presence of magnetic moments. In this study, we have used DFT-based calculations to scrutinise the paramagnetic/ferromagnetic (FM) as well as metallic/semiconducting behavior of these HH compounds. The predicted phase stability using the energy versus volume curves reveals that they are stable in Type C phase. RuTiSi and RuTiGe are found to be stable in the paramagnetic phase whereas RuTiSn is stable in the FM phase with a finite value of magnetic moment. The electronic band structures and density of states (DOS) plots predict that the studied compounds belong to [Formula: see text]-type degenerate semiconductors as the Fermi Level lies within the valence band. Due to the existence of finite DOS at the Fermi level, they show an enhanced metallic behavior. A small value indirect gap is found between valence band maximum (VBM) and conduction band minimum (CBM) in all these studied RuTiX HH alloys depicting their semiconducting nature. The elastic constants of cubic phase are computed for the first time and they obey the mechanical stability criteria. The positive value of [Formula: see text] and value of [Formula: see text]/[Formula: see text] ratio of these HH compounds exhibit their ductile nature. The thermoelectric properties of these compounds are investigated, and a comparatively higher figure of merit reveals their scope of application in thermoelectric devices.

Insights into structural stability, electronic structure, and elastic and thermodynamic properties of A15-type Mo3X (X = Si, Ge, and Sn) compounds based on first-principles predictions

In this study, we performed first-principles calculations based on density functional theory to investigate the structure, electronic properties, and elastic and thermodynamic performance of A15-type Mo3X (X = Si, Ge, and Sn) molybdenum-based compounds. The calculated formation enthalpies indicate that all of these Mo3X compounds exhibit thermodynamic stability. The electronic properties of Mo3X, including the band structures, density of states, and electron density difference, indicate that these compounds are metallic. Moreover, the Mo–Mo bonds are covalent whereas the Mo-X bonds are mixed ionic–covalent. The elastic properties of Mo3X compounds were predicted based on the single-crystal and polycrystal elastic moduli. In addition, the anisotropy of elasticity was determined using the elastic anisotropy indexes, three-dimensional surface constructions, and two-dimensional projections. Finally, we explored the thermodynamic parameters, including the Debye temperatures and minimum thermal conductivities. The order of the minimum thermal conductivity was determined as: Mo3Si > Mo3Ge > Mo3Sn.

Co–Ge compounds and their electrochemical performance as high-performance Li-ion battery anodes

Representative Ge-rich binary Co–Ge compounds (CoGe, Co5Ge7, and CoGe2) are synthesized by facile solid-state reactions and apply as Li-ion battery (LIB) anode materials. Among the binary Co–Ge compounds studied, CoGe2 shows the highest Li reversibility. Thus, a CoGe2-decorated carbon composite (CoGe2@C) is prepared to improve the electrochemical performance of CoGe2. Ex situ analysis results of X-ray diffraction and extended X-ray absorption fine structure demonstrate that the CoGe2@C has an interesting mechanism of conversion/recombination during Li insertion/extraction. Owing to this continual conversion/recombination mechanism during cycling, the CoGe2@C shows superior electrochemical performance. Specifically, CoGe2@C shows high reversible capacity (1,106 and 973 mAh/cm3 at current density of 50 and 100 mA/g, respectively), stable cycling behavior (93.3% and 98.8% capacity retention at a cycling rate of 50 mA/g and 100 mA/g, respectively, after 100 cycling), and fast rate capability with stable cycling behavior (~700 mAh/cm3 at 1C rate over 200 cycles). Therefore, CoGe2@C can be used as a high-performance LIB anode material.

First Principle Study of Structural, Electronic, Elastic, and Magnetic Properties of Half-Heusler Compounds ScTiX (X = Si, Ge, Pb, In, Sb, and Tl)

Herein, we report the study of half-Heusler ScTiX (X = Si, Ge, Pb, In, As, and Tl) compounds for the first time employing the scheme of density functional theory (DFT). The influence of on-site Coulomb interactions is taken into account, and simulations are conducted in generalized gradient approximation with the added Hubbard U term (GGA + U). All the compounds were observed to have a narrow band gap on the spin-down configuration. Though spinning the majority channel (spin-up), it is found to be metallic. Consequently, all compounds are semi-metallic or half-metallic and 100% of spin polarized at the Fermi level. Various features, comprising structural, magnetic, elastic, and electronic properties, are calculated through full-potential linearized augmented plane wave (FP-LAPW) method, since they are incorporated in the computer simulation package of WIEN2k. Equilibrium lattice constants are observed for all the compounds which exist within the domain of 6.4–6.8 A°. The IRelast package is already integrated in WIEN2K that has been used for the elastic properties. Elastic features reflect the brittle character of all the material. The total magnetic moments for all such materials are greater than 3 μB, i.e., 3 μB of MTot. Therefore, the compounds show a strong ferromagnetic behavior. These are therefore expected to be used as shape base for thin layers within metastable situations for spintronic applications. The resulted elastic properties show that ScTiSi is ductile, while all other five compounds represent brittle nature. Above findings delight the prospect of ScTiX (X = Si, Ge, Pb, In, As and Ti) compounds in developing half-metallic HH compounds for spintronics and memory storage appliances.

Novel Si(II)+ and Ge(II)+ Compounds as Efficient Catalysts in Organosilicon Chemistry: Siloxane Coupling Reaction

Novel catalytically active cationic Si(II) and Ge(II) compounds were synthesized and isolated in pure form. The Ge(II)+-based compounds proved to be stable against air and moisture and therefore can be handled very easily. All compounds efficiently catalyze the oxidative coupling of hydrosil(ox)anes with aldehydes and ketones as oxidation reagents and simultaneously the reductive ether coupling at very low amounts of <0.01 mol %. Because the catalysts also catalyze the reversible cyclotrimerization of aldehydes, paraldehyde can be used as a convenient source for acetaldehyde in siloxane coupling. It is shown that the reaction is especially suitable to make siloxane copolymers. Moreover, a new fluorine-free weakly coordinating boronate anion, B(SiCl3)4–, was successfully combined with the Si(II) and Ge(II) cations to give the stable catalytically active ion pairs Cp*Si:+B(SiCl3)4–, Cp*Ge:+B(SiCl3)4–, and [Cp(SiMe3)3Ge:+]B(SiCl3)4–.

Effects of interstitial C atoms on magnetostructural transformation and magnetocaloric effect in MnNi0.77Fe0.23GeCx compounds

In this study, the influence of interstitial C atoms on the magnetostructural transformation and magnetocaloric effect in MnNi0.77Fe0.23GeCx (x = 0, 0.02, and 0.03) compounds has been investigated. The introduction of C atoms into the interstitial sites of the MnNi0.77Fe0.23Ge compounds leads to the enhanced stability of the orthorhombic phase, thus enhancing the structural transition temperature. Moreover, the critical field of antiferromagnetic (AFM)–ferromagnetic (FM) conversion significantly decreases following C atom incorporation. Therefore, it can be inferred that C atoms can promote the AFM–FM conversion in the TiNiSi-type orthorhombic phase. The MnNi0.77Fe0.23GeCx compound with x = 0.02 exhibits a large magnetocaloric effect due to the ferromagnetic magnetostructural transition. Furthermore, for the compound with x = 0.03, a table-like magnetocaloric effect is observed around room temperature owing to the coupling of the martensitic and metamagnetic transitions, which confirms the wide working temperature range and a large refrigerant capacity.