Stable Solid Compounds Research Articles

Enhancing growth speed of 3C–SiC using solution growth method by a new low temperature Mn-based cosolvent

Solution growth is a promising method for rapidly and stably preparing high-quality silicon carbide (SiC) single crystals. However, the coexistence of polycrystalline parasitism and solid inclusions during the growth of SiC in high-temperature solutions above 1800 °C still poses a serious threat to the quality of single crystals. Herein, we introduce an innovative Mn-based cosolvent for controlling the stable and fast growth of cubic-type silicon carbide (3C–SiC) single crystals at low temperatures. Firstly, our thermodynamic analysis reveals that SiC is the only stable solid compound in the low-temperature solution (1500–1600 °C) of the Si–Mn–C system, which is an important condition for the stable growth of crystals. Compared to typical solvents like Si–Cr, Si–Ti, and Si–Fe, the Si–Mn solvent exhibits the highest solubility and supersaturation for carbon. Secondly, our solubility calculations of SiC in the solvent show that the Mn-rich solvent can significantly increase the solubility of SiC. Thirdly, we successfully grew 3C–SiC single crystals from Si–Mn solution at 1500 °C without other SiC polymorphs produced. Rapid growth of SiC crystals in Mn-rich solution was achieved by modulating the content of Mn. Our work highlights the superiority of Si–Mn cosolvents in facilitating rapid growth of 3C–SiC single crystals at low temperatures. It introduces a novel approach by applying phase diagram calculation techniques to design suitable solvent systems for the solution growth of SiC single crystals.

A first-principles study of the structural, electronic and elastic properties of the FeO2-FeO2He system under high pressure.

The origin of the wave velocity anomalies at the core-mantle boundary (CMB) has been controversial. The primordial helium reservoir in the deep lower mantle remains elusive even with geochemical evidence for its existence. Here, we calculated the density and wave velocity of the FeO2-FeO2He system under the CMB conditions using first principles. The FeO2 and FeO2He of pyrite-type can exist stably under the CMB conditions without melting, and the incorporated helium increases the stability of the system. The electrical properties of FeO2 and FeO2He are not related to pressure. Doped helium reduces the density of the system but increases the elastic modulus. Our results suggest that FeO2 can be used as a viable material composition of ultra-low velocity zones (ULVZs), and FeO2He can explain the D'' seismic discontinuity instead of ULVZs. The primordial helium reservoir possibly formed by the accumulation of FeO2He, the only stable solid helium-bearing compound under the CMB conditions, may coincide with the location of the D'' layer.

Effect of phosphogypsum use as a waste recycling on GHG emissions by mineral carbonisation method

The release of greenhouse gas emissions into the atmosphere as a result of anthropogenic sources and industrial applications has triggered the increase in global temperatures called global warming and related climate change. Phosphogypsum (PG) is a by-product of the wet process phosphoric acid (H3PO4) production process, which chemically consists of calcium sulfate dihydrate (CaSO4·2H2O) with some impurities. Annual PG accumulation has reached 300 Mtons and a strategy is needed to ensure efficient, continuous and bulk consumption. Due to the high amount of calcium it contains, PG is a material suitable for use in CO2 capture and storage processes to form stable solid carbonate compounds. This process, called mineral carbonisation of PG, contributes to sustainable development goals by providing the multiple benefits of both the utilisation of an industrial by-product and the realisation of CO2 capture and storage technology.

Pressure-stabilized structures of water-neon system under high pressure

Neon (Ne), as the fifth most abundant element in the universe, is rare to react with other elements by forming stable solid compounds. It is well known that pressure is a powerful tool to generate the compounds that are inaccessible at ambient pressure. In this work, we performed structure-searching simulations to examine stable compounds of Ne and ${\mathrm{H}}_{2}\mathrm{O}$ at a wide pressure range of 0--600 GPa. Our simulations identified two phases of ${\mathrm{H}}_{2}\mathrm{ONe}$ and ${\mathrm{H}}_{2}{\mathrm{ONe}}_{2}$ under high pressure. By employing chemical-bonding analysis, interestingly, we found that Ne-O interactions are comparable in strength to that of conventional hydrogen bond. Moreover, our molecular dynamic simulations indicate the diffusion behavior of hydrogen atoms within a fixed Ne-O lattice framework of ${\mathrm{H}}_{2}{\mathrm{ONe}}_{2}$ at high pressure and high temperature. These results provide the implications for the possible existence of pressure-stabilized ${\mathrm{H}}_{2}\mathrm{ONe}$ and ${\mathrm{H}}_{2}{\mathrm{ONe}}_{2}$ compounds viable in a variety of astronomical objects.

Gluconic acid promoted cascade reactions of 2-phenylimidazo[1,2-a] pyridine-3-carbaldehyde with cyclohexane-1,3-dione to create novel fused bisheterocycles

Here in, we described the synthesis of novel bisheterocycles imidazopyridine bearing xanthenedione by reacting various substituted 2-phenylimidazo [1,2-a] pyridine-3-carbaldehyde with cyclohexane-1,3-dione in gluconic acid aqueous solution (GAAS) via a tandem Knoevenagel followed by Michael, cyclization & tautomerization sequence. The use of GAAS in organic synthesis offers significant benefits like cost-effective, simple operation, reusable catalyst and green method. The reaction completed in 2–12 h to afford white stable solid compounds with very good yield. The structures of the compounds are confirmed by analyzing MS, IR, 1H NMR and 13C NMR spectra. Further, the structure of compound 3 h was confirmed by XRD analysis.

Calcium-Based Sustainable Chemical Technologies for Total Carbon Recycling.

Calcium carbide, a stable solid compound composed of two atoms of carbon and one of calcium, has proven its effectiveness in chemical synthesis, due to the safety and convenience of handling the C≡C acetylenic units. The areas of CaC2 application are very diverse, and the development of calcium-mediated approaches resolves several important challenges. This Review aims to discuss the laboratory chemistry of calcium carbide, and to go beyond its frontiers to organic synthesis, life sciences, materials and construction, carbon dioxide capturing, alloy manufacturing, and agriculture. The recyclability of calcium carbide and the availability of large-scale industrial production facilities, as well as the future possibility of fossil-resource-independent manufacturing, position this compound as a key chemical platform for sustainable development. Easy regeneration and reuse of the carbide highlight calcium-based sustainable chemical technologies as promising instruments for total carbon recycling.

Reactivity of\xa0He with\xa0ionic compounds under high pressure

Until very recently, helium had remained the last naturally occurring element that was known not to form stable solid compounds. Here we propose and demonstrate that there is a general driving force for helium to react with ionic compounds that contain an unequal number of cations and anions. The corresponding reaction products are stabilized not by local chemical bonds but by long-range Coulomb interactions that are significantly modified by the insertion of helium atoms, especially under high pressure. This mechanism also explains the recently discovered reactivity of He and Na under pressure. Our work reveals that helium has the propensity to react with a broad range of ionic compounds at pressures as low as 30 GPa. Since most of the Earth’s minerals contain unequal numbers of positively and negatively charged atoms, our work suggests that large quantities of He might be stored in the Earth’s lower mantle.

First-principles molecular dynamics study of deuterium diffusion in liquid tin.

Understanding the retention of hydrogen isotopes in liquid metals, such as lithium and tin, is of great importance in designing a liquid plasma-facing component in fusion reactors. However, experimental diffusivity data of hydrogen isotopes in liquid metals are still limited or controversial. We employ first-principles molecular dynamics simulations to predict diffusion coefficients of deuterium in liquid tin at temperatures ranging from 573 to 1673 K. Our simulations indicate faster diffusion of deuterium in liquid tin than the self-diffusivity of tin. In addition, we find that the structural and dynamic properties of tin are insensitive to the inserted deuterium at temperatures and concentrations considered. We also observe that tin and deuterium do not form stable solid compounds. These predicted results from simulations enable us to have a better understanding of the retention of hydrogen isotopes in liquid tin.

Helium Chemistry: React with nobility.

Helium, the 'most noble' of the noble gases, had only been coaxed into forming molecular ions or van der Waals compounds. It has now been seen in a stable solid compound, Na2He, under high pressure.

Synthesis and Structure of 1,2‐Dimethylene[2.10]metacyclophane and Its Conversion into Chiral [10]Benzenometacyclophanes

Bromination of 5,21‐di‐tert‐butyl‐8,24‐dimethoxy‐1,2‐dimethyl[2.10]metacyclophan‐1‐ene (MCP‐1‐ene; 1) with benzyltrimethylammonium tribromide exclusively afforded 1,2‐bis(bromomethyl)‐5,21‐di‐tert‐butyl‐8,24‐dimethoxy[2.10]MCP‐1‐ene (2). Debromination of 2 with Zn and AcOH in CH2Cl2 solution at room temperature for 24 h produced dimethylene[2.10]MCP 7 in 92 % yield, which is a stable solid compound. Compound 7 was treated with dimethyl acetylenedicarboxylate (DMAD) to provide 1,2‐(3′,6′‐dihydrobenzo)‐5,21‐di‐tert‐butyl‐8,24‐dimethoxy[2.10]MCP‐4′,5′‐dimethylcarboxylate (8) in good yield. Diels–Alder adduct 8 was converted into a novel and inherently chiral areno‐bridged dimethoxy[2.10]MCP‐4′,5′‐dimethylcarboxylate 9, possessing C1 symmetry, by aromatization with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ). A new type of N‐phenyl‐maleimide substituted 1,2‐(3′,6′‐dihydrobenzo)‐5,21‐di‐tert‐butyl‐8,24‐dimethoxy[2.10]MCP‐4′,5′‐N‐phenylmaleimide 10 was also synthesized from 7 through treatment with N‐phenylmaleimide in toluene at 110 °C followed by aromatization with DDQ. Single‐crystal X‐ray analysis of 9 revealed the formation of a syn‐isomer.

Synthesis, characterization and stability of Cr(III) and Fe(III) hydroxides

Chromium is a common contaminant of soils and aquifers and constitutes a major environmental problem. In nature, chromium usually exists in the form of two oxidation states, trivalent, Cr(III), which is relatively innocuous for biota and for the aquatic environment, and hexavalent, Cr(VI) which is toxic, carcinogenic and very soluble. Accordingly, the majority of wastewater and groundwater treatment technologies, include a stage where Cr(VI) is reduced to Cr(III), in order to remove chromium from the aqueous phase and bind the element in the form of environmentally stable solid compounds. In the absence of iron the final product is typically of the form Cr(OH)3·xH2O whereas in the presence of iron the precipitate is a mixed Fe(1−x)Crx(OH)3 phase. In this study, we report on the synthesis, characterisation and stability of mixed (Fex,Cr1−x)(OH)3 hydroxides as compared to the stability of Cr(OH)3. We established that the plain Cr(III) hydroxide, abiding to the approximate molecular formula Cr(OH)3·3H2O, was crystalline, highly soluble, i.e. unstable, with a tendency to transform into the stable amorphous hydroxide Cr(OH)3(am) phase. Mixed Fe0.75Cr0.25(OH)3 hydroxides were found to be of the ferrihydrite structure, Fe(OH)3, and we correlated their solubility to that of a solid solution formed by plain ferrihydrite and the amorphous Cr(III) hydroxide. Both our experimental results and thermodynamic calculations indicated that mixed Fe(III)–Cr(III) hydroxides are more effective enhancers of groundwater quality, in comparison to the plain amorphous or crystalline Cr(III) hydroxides, the latter found to have a solubility typically higher than 50μg/l (maximum EU permitted Cr level in drinking water), while the amorphous Cr(OH)3(am) phase was within the drinking water threshold in the range 5.7<pH<11. In comparison, the mixed Fe0.75Cr0.25(OH)3 hydroxides studied were of extended stability in the 4.8<pH<13.5 range.

Synthesis and Characterization of New Nickel(II) Chelates With S-Alkyl-Salicylaldehyde Thiosemicarbazones

The template reactions of salicylidene-, 5-bromosalicylidene-, and 3,5-dichlorosalicylidene-S-R-thiosemicarbazone (R: propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, dodecyl) with 5-bromo- and 3,5-dichlorosalicylaldehyde in the presence of nickel(II) yielded N1,N4-diarylidene-S-alkyl-thiosemicarbazone chelates. The N2O2 type complexes were isolated as stable solid compounds and characterized by elemental analysis, electronic, infrared, 1H NMR, and mass spectroscopies. The magnetic susceptibility measurements at room temperature (r.t.) indicate the diamagnetic nature of the complexes. The relationship between melting point (mp) values of the nickel(II) template complexes and the chain length of alkyl moiety was clearly shown. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the related elements to view the free supplemental file.

Phase behavior and crystal structure of 3-(1-naphthyloxy)- and 3-(4-indolyloxy)-propane-1,2-diol, synthetic precursors of chiral drugs propranolol and pindolol

Valuable precursors of popular chiral drugs propranolol and pindolol, 3-(1-naphthyloxy)-propane-1,2-diol 3 and 3-(4-indolyloxy)-propane-1,2-diol 4 were investigated by IR spectroscopy, DSC, and X-ray diffraction methods. Both compounds, crystallizing from enantiopure feed material, form “guaifenesin-like” crystal packing in which the classic H-bonded bilayers, framed in both sides by hydrophobic fragments of the molecules, acts as the basic crystal-forming motif. Diol 4 prone to spontaneous resolution and conserves its packing pattern crystallizing from racemate. Under the same conditions, diol 3 forms weakly stable solid racemic compound. Some reasons for such a behavior are identified and discussed.

Crystal structure and phase behavior of the tolyl glycerol ethers. From the conglomerate former to the chirality-driven nanogelator

According to differential scanning calorimetry data ortho-, meta-, and para-tolyl glycerol ethers 1–3 form thermodynamically most stable crystal phases during solution crystallization. For all members of the series the crystal phases formed during melt crystallization have different thermodynamic characteristics from those of the stable ones. Binary melting diagrams were constructed for the stable solid phases; on this basis it was found that 1 is prone to spontaneous resolution, and 2 and 3 form stable solid racemic compounds, the Gibbs energy of formation for which are found to be −2.70 and −2.43 kJ mol−1. Solution grown single crystals of 1–3 were investigated by an X-ray diffraction method. The principal supramolecular crystal formative motifs were revealed: 1D columns for 1 and scal-2, 2D bilayers having developed a 2D system of intermolecular hydrogen bonds (IMHB) for rac-2 and rac-3, and 2D bilayer having 1D spiral IMHB organization for scal-3. The possible reasons preventing the solid racemic compound formation in the case of 1, and the spontaneous resolution manifestation in the cases of 2 and 3 are disclosed. It was demonstrated that, from the whole family of tolyl glycerol ethers, only scal-3 samples are capable of supramolecular gels formation. This property is connected with the peculiarities of the scalemic 3 crystal packing.

Half-metallic magnetism of Co 2CrX (X=As, Sb) Heusler compounds: An ab initio study

In this study, we present the electronic, magnetic, and structural properties of two novel half-metallic full-Heusler compounds, Co 2CrAs and Co 2CrSb, in cubic L2 1 geometry. The calculations are based on the density functional theory within plane-wave pseudopotential method and spin-polarized generalized gradient approximation of the exchange-correlation functional. The electronic band structures and density of states of the systems indicate half-metallic behavior with vanishing electronic density of states of minority spins at Fermi level, which yields perfect spin polarization. The calculated magnetic moments of both systems in L2 1 structure are 5.00 μ B , which are largely localized on the chromium site. The energy gaps in minority spin states are restricted by the 3d-states of cobalt atoms on two different sublattices. The formation enthalpies for both structures are negative indicating stability of these systems against decomposition into stable solid compounds.

Free enthalpy landscape of SrO

Trying to predict thermodynamically stable and metastable solid compounds as function of pressure and temperature requires the global exploration of the enthalpy landscapes of chemical systems and the subsequent construction of their free enthalpy landscapes. In this work, we present a general approach to the determination of a free energy landscape. As an example, we construct the free enthalpy landscape of SrO for two different pressures on the empirical potential level and also compute various thermodynamic and elastic properties of SrO in the NaCl-, CsCl-, NiAs-, NbS-, TiP-, beta-BeO, sphalerite-, and wurtzite-structure type on an ab initio level. We employ density functional theory within the hybrid B3LYP approximation. The results show good agreement with experimental and theoretical data.

Novel lanthanide complexeswith di-2-pyridyl ketone-p-chloro-benzoylhydrazone

The reaction of a hydrated nitrate salt of lanthanide(III) (Ln=Er, Ho, Tb, Gd) or yttrium(III) (Y) with the ligand di-2-pyridyl ketone-p-Cl-benzoylhydrazone (DpkClBH), afforded air stable solid compounds. The new complexes characterized by means of elemental analysis (C, H, N, Ln), magnetic moment determinations and spectroscopic data (IR, MS). It is proposed that they are cationic of the general type: [Ln(DpkClBH)2(NO3)2]NO3·nH2O, (n=2, 1, 1, 1, 1.5 for Ln=Y, Gd, Tb, Ho, Er, respectively).

Solid-Liquid Equilibrium in the Systems with an Ionic Liquid

An active interest in ionic liquids has grown over the last years. This relatively new class of solvents appears to be potentially useful as a "greener" alternative to volatile organic compounds. This work was aimed at studying the effect of addition of the ionic liquid 1-butyl-3-methylimidazolium chloride to two systems (acetic acid (1)-formamide (2) and propionic acid (1)-formamide (2)) on formation of a compound in the solid phase. In previous work, the presence of a solid compound with a formula (CH3COOH)2·HCONH2 was investigated in the binary system acetic acid (1)-formamide (2) and a stable solid compound with a different formula CH3CH2COOH·(HCONH2)2 was found in the binary system propionic acid (1)-formamide (2). In both cases the compound formation is attributed to a strong cross-association (O···H···N). Solid-liquid equilibrium of the systems measured in this work was determined from time-temperature warming curves. In both measured ternary systems with a small addition of the ionic liquid 1-butyl-3-methylimidazolium chloride (i.e. the systems acetic acid (1)-formamide (2)-1-butyl-3-methylimidazolium chloride (3) and propionic acid (1)-formamide (2)-1-butyl-3-methylimidazolium chloride (3)) the above mentioned stable solid compounds are formed and the corresponding melting temperature of these compounds decreased. Dissociation parameters were modelled thermodynamically for solid adducts.

Aluminumdodecatungstophosphate (AlPW 12O 40) as a reusable Lewis acid catalyst : Facile regioselective ring opening of epoxides with alcohols, acetic acid and thiols

AlPW 12O 40 as a recyclable Lewis acid and stable solid compound was introduced for efficient ring opening of different epoxides with thiols, acetic acid, and primary, secondary, and tertiary alcohols. These processes were carried out at room temperature with high regio- and stereoselectivity.

Oxovanadium(IV) complexes of bromo-and methoxy substituted N1,N4-diarylidene-S-methylthiosemicarbazones

AbstractFour new oxovanadium(IV) compounds were prepared by template reaction of salicyl-, 5-bromosalicyl-and 3-methoxysalicyl-aldehyde S-methylthiosemicarbazones with 2-hydroxy-, 5-bromo-2-hydroxy-and 3-methoxy-2-hydroxy-benzaldehyde in various combinations. The compounds were isolated as stable solid compounds with general formula [VO(L)] and characterized by elemental analysis, conductivity and magnetic measurements, electronic, IR and EPR spectroscopy. The X-band EPR signals recorded from powder forms of all samples have a single asymmetric line shape and theoretical fit studies proved the presence of axial symmetry around the paramagnetic vanadium ions. The anisotropic Lande splitting factors take values of g‖ &lt; g⊥ &lt; ge = 2.0023. Orbital energy levels for magnetic electrons were determined from theoretically well fitted Spin Hamiltonian parameters. The EPR spectra recorded from solution forms almost have isotropic character.