Blende Type Research Articles

On-the-fly training of polynomial machine learning potentials in computing lattice thermal conductivity.

The application of first-principles calculations for predicting lattice thermal conductivity (LTC) in crystalline materials, in conjunction with the linearized phonon Boltzmann equation, has gained increasing popularity. In this calculation, the determination of force constants through first-principles calculations is critical for accurate LTC predictions. For material exploration, performing first-principles LTC calculations in a high-throughput manner is now expected, although it requires significant computational resources. To reduce computational demands, we integrated polynomial machine learning potentials on-the-fly during the first-principles LTC calculations. This paper presents a systematic approach to first-principles LTC calculations. We designed and optimized an efficient workflow that integrates multiple modular software packages. We applied this approach to calculate LTCs for 103 compounds of wurtzite, zinc blende, and rocksalt types to evaluate the performance of the polynomial machine learning potentials in LTC calculations. We demonstrate a significant reduction in the computational resources required for the LTC predictions.

High-Cd sphalerite in the Pangxidong Pb-Zn-Ag deposit (Yunkai Domian, South China): Insight for physicochemical condition of orogenic-type deposit

The Pangxidong Pb-Zn-Ag-(Au) deposit is one of the representative orogenic-type Au-bearing polymetallic deposits in the Yunkai Domian, Cathaysia Block, South China, and both its vein- and altered rocks-type orebodies are controlled by the regional NE-trending Bobai-Cenxi Fault and its subordinate faults. Metallogenic potential of critical metals, such as Cd, In, Ga and Ge, hosted in these orogenic-type polymetallic deposits, have never been evaluated. We, therefore, selected the Pangxidong to conduct a series of field survey, microscopic observation, electron probe micro-analyzer (EPMA) and laser ablation inductively coupled plasm mass spectrometer (LA-ICP-MS) investigation. We identified two generations of sphalerite with different mineral assemblages and mineralogical features, and both sphalerite generations have the relatively higher Cd, Cu, Ag and Au contents, against the lower Ga, Ge, In and Sn contents. Notably, an extremely elevated Cd content was detected in the earlier SpA (4869–47194 ppm, mean = 15976 ppm), against those in the later SpB (5629–9980 ppm, mean = 7224 ppm). Further temperature evaluation using GGIMFis geothermometer indicates that the earlier SpA (229–367 ℃, mean = 239 ℃) have a slightly higher crystallization temperature than the later SpB (228–240 ℃, mean = 233 ℃). Collectively, we highlight that the Pangxidong sphalerite have different minor and trace element associations and concentrations against most other Zn-Pb deposit styles such as MVT and skarn system, and therefore represents a novel sphalerite type from the orogenic-type deposit.

Investigating the properties of a ZnSe-based solid solution at 2.0 GPa

In this work, ZnSe-based polycrystalline ceramics were successfully synthesized from Se and Zn powders in the range of 2.0 GPa and 900 °C–1400 °C by using the high-pressure and high-temperature (HPHT) method. From the acquired experimental results, it was revealed that the fabricated samples were composed of ZnSe with a sphalerite structural type. More specifically, the samples consisted of lamellar and granular grains, and the stomata of the samples showed a trend of first increasing and then decreasing as a function of the elevated temperature. In addition, the infrared transmittance of ZnSe ceramics in the 4 to 18-μm range increased and then decreased by increasing the temperature. When the temperature exceeded the value of 1000 °C, the internal zinc surplus and selenium deficiency of zinc selenide ceramics induced a decrease in the mechanical and optical properties of the ceramics. By optimizing the conditions of the experimental process, the ZnSe synthesized at 1300 °C exhibited better performance with a transmittance of 55%.

Ore-forming processes of the Baisong carbonate-hosted Pb-Zn deposit, SW China: Constraints from in-situ sphalerite trace element and sulfide S-isotopic compositions

The western Hunan-eastern Guizhou (WHEG) Pb-Zn ore belt in the southwestern Yangtze block is a main Pb-Zn province in China. The metallogenic characteristics of this ore belt were widely reported, but the ore-forming process is still poorly understood. The lower Cambrian carbonate-hosted Baisong deposit is a representative Pb-Zn deposit in the southern WHEG belt. Sphalerite trace elements and sulfur isotopic compositions from the Baisong Pb-Zn deposit could reveal the ore-forming fluid source and metallogenic processes. Four types of sphalerites have been distinguished (black colloidal sphalerite (Sp) I, light-colored sector Sp II, red zoned Sp III and brown zoned Sp IV, indicating four sulfide mineralization stages from the early ore phase. Sp I (66-117℃, δ34S: +24.8 to + 27.8‰) has the highest Cd-Ga-Ag-Cu contents among the four sphalerite types, and commonly overgrow with marcasite. This suggests that Sp I was formed from acidic fluids under high precipitation rate. The trace elements and sulfur isotopic compositions of Sp II (80-128℃, δ34S: +26.5 to + 28‰) are similar to Sp I. Sp II was likely formed by a decrease in oversaturation and precipitation rate with fluid pH increase. Sp III (127-164℃, δ34S: +31 to + 32.5‰), commonly overgrow on pyrite (Py I), has higher Mn-Fe-Ge but lower Cd-Cu-Ga-Ag contents and heavier sulfur isotopes than Sp II. Changes in precipitation environment and fluid compositions are likely major factors in forming Sp III (temperature increase, pH increase and more reduced). The forming of Sp III and Py I likely consumed the Fe and Ge in the fluid, depriving those elements from the later-formed Sp IV (97-141℃, δ34S: +25.7 to + 29.8‰). The sulfide δ34S value (+22.5 to + 46.3‰) implies that the S2- at Baisong was sourced from seawater sulfates via thermochemical sulfate reduction (TSR). Sphalerite trace element features reflect that the Baisong is an MVT deposit.

Ultraviolet-photoluminescence and trace element analyses in Ga-rich sphalerite from the Djebel Gustar Zn-Pb deposit, Algeria

The Djebel Gustar Zn-Pb deposit in northeastern Algeria is one of many carbonate-hosted base metal deposits in the Atlas metallogenic province of North Africa. The sphalerite in this deposit occurs in five distinct types that differ in texture, mineral assemblage, chemical composition, and UV photoluminescence signature. Detailed investigation of trace elements by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) showed that the sphalerite is significantly enriched in the critical metal Ga. The trace element concentrations of the different sphalerite types correlated well with their photoluminescence color; with Mn2+ (orange-yellow), Cu+ (green), and Ga3+ (red) being the dominant activators. We suggest that the Ga enrichment in the Djebel Gustar deposit is the result of formation conditions that include the mixing of a Cl-rich fluid carrying mainly Zn and Pb with a more reduced and Cl-poor fluid containing considerable organic matter and/or calcite with adsorbed Ga(OH)3. This Ga was subsequently incorporated into sphalerite, rather than forming a stoichiometric Ga phase. Furthermore, our study demonstrates that UV photoluminescence of low Fe sphalerite has the potential to become a simple and affordable tool for preliminary characterization of sphalerite ores in mining and exploration with respect to critical elements such as Ga.

Рост пленок SiC, AlN и GaN на кремниевых изделиях произвольной геометрии для микроэлектромеханических применений

A technique is proposed for the formation of epitaxial films of silicon carbide, gallium and aluminum nitrides on the surface of non-planar silicon parts. Using the technique, a GaN/AlN/SiC/Si heterostructure was grown on the surface of a silicon ring. The samples were studied by scanning electron microscopy, as well as raman and energy dispersive spectroscopy. It is shown that the preliminary deposition of a SiC layer on silicon by the atomic substitution method, in which (111) facets are inevitably being formed regardless of the local crystallographic orientation of the substrate surface, makes it possible to efficiently grow subsequent layers of III-nitrides of both wurtzite and sphalerite types on silicon parts.

Polarity-extended 8 - Neff rule for semiconducting main-group compounds with the TiNiSi-type of crystal structure.

Application of chemical bonding analysis in position-space techniques based on combined topological analysis of the electron density and electron-localizability indicator distributions has recently led to the formulation of a polarity-extended 8 - Neff rule for consistent inclusion of quantum chemically obtained polar-covalent bonding data into the classical 8 - N scheme for main-group compounds. Previous application of this scheme to semiconducting main-group compounds of the cubic MgAgAs type of structure with 8 valence electrons per formula unit (8 ve per f.u.) has shown a covalent bonding tendency preferring one zinc blende type partial structure over the other one, which seems to corroborate the classical Lewis picture of maximally four covalent bonds per main-group element. In contrast to the MgAgAs type, the orthorhombic TiNiSi type of structure displays a much higher geometrical flexibility to incorporate different kinds of metal atoms. The analysis of polar-covalent bonding in semiconducting 8 ve per f.u. containing main-group compounds AA'E of this structure type reveals a transition to non-Lewis type bonding scenarios of species E with up to ten polar-covalently bonded metal atoms. This kind of situation is consistently included into the extended 8 - Neff type bonding scheme. A systematic increase of partially covalent bonding from chalcogenides E16 to the tetrelides E14 is found, summing up to as much as 2 covalent bonds E14-A and E14-A', and correspondingly remaining 4 lone pair type electrons on species E14. The familiar notion of this structure type consisting of a '[NiSi]'-type framework with 'Ti'-type atoms filling the voids cannot be supported for the compounds investigated.

Time-resolved in-situ investigation of Co-nitride thin film growth by grazing incidence X-ray absorption spectroscopy

The growth of cobalt nitride thin films prepared by reactive sputtering on float glass substrates was in-situ investigated using surface sensitive, grazing incidence X-ray absorption fine structure spectroscopy. Time-resolved measurements employing a quick-scanning monochromator allow to follow the growth on time-scales of a few seconds per spectrum, so that the film growth could be studied in detail. A quantitative modeling of the obtained data clearly show that a zinc blende type CoN is formed already during the initial stages of film growth, and the formation of small crystalline clusters finally lead to a 3D-growth of polycrystalline CoN-films.

Study on the decomposition of CuI films due to defect state instability

Cuprous(Ⅰ) iodide (CuI) is widely used as a conducting material in various optoelectronic devices. However, defect properties and instabilities lead to changes in the semiconductor properties of CuI, which seriously affects the stability of related optoelectronic devices. Therefore, in this paper, the decomposition and defect state properties of CuI films are investigated in depth. CuI was prepared by a simple iodination method and belongs to the zinc blende type structure, preferentially crystallizing along the (111) direction. Microscopic tests reveal that grains in CuI film are tightly bonded without obvious cracks or holes, and the grain size reaches 1.231 μm. In the subsequent spectral analysis, multiple emission peaks (free exciton and defect emission peak) were obtained by Gaussian fitting. The two major point defects (Cu vacancy (VCu) and I vacancy (VI)) in CuI were analyzed theoretically, and the calculated defect energy levels matched the energies of the emission peaks. The results of Gaussian waveform fitting and density functional calculations indicate the presence of VCu defects and VI defects in CuI. Significant variations in emission and electrical properties were observed in successive tests, indicating the relatively poor long-term stability of the CuI samples. The changes in the emission characteristics are mainly manifested by the weakening of the 416 nm emission and the enhancement of the 720 nm emission, while the changes in the electrical characteristics are mainly manifested by the increasing resistance. The above changes are attributed to the concentration of defect states, mainly due to the increase of VI defects and the decrease of VCu defects, hence the severe iodine decomposition occurs in the CuI samples. To inhibit the decomposition, three schemes (multiple iodination, multilayer iodination, and encapsulation) were proposed, and relevant experiments were conducted.

Cubic Stuffed-Diamond Semiconductors LiCu3TiQ4 (Q = S, Se, and Te).

Lithium chalcogenides have been understudied, owing to the difficulty in managing the chemical reactivity of lithium. These materials are of interest as potential ion conductors and thermal neutron detectors. In this study, we describe three new cubic lithium copper chalcotitanates that crystallize in the P4̅3m space group. LiCu3TiS4, a = 5.5064(6) Å, and LiCu3TiSe4, a = 5.7122(7) Å, represent two members of a new stuffed diamond-type crystal structure, while LiCu3TiTe4, a = 5.9830(7) Å crystallized into a similar structure exhibiting lithium and copper mixed occupancy. These structures can be understood as hybrids of the zinc-blende and sulvanite structure types. In situ powder X-ray diffraction was utilized to construct a "panoramic" reaction map for the preparation of LiCu3TiTe4, facilitating the design of a rational synthesis and uncovering three new transient phases. LiCu3TiS4 and LiCu3TiSe4 are thermally stable up to 1000 °C under vacuum, while LiCu3TiTe4 partially decomposes when slowly cooled to 400 °C. Density functional theory calculations suggest that these compounds are indirect band gap semiconductors. The measured work functions are 4.77(5), 4.56(5), and 4.69(5) eV, and the measured band gaps are 2.23(5), 1.86(5), and 1.34(5) eV for the S, Se, and Te analogues, respectively.

Growth Kinetics and Optical Proprties of CdSe Nanocrystals

We were synthesized CdSe nanocrystals (NC) at a temperature of 260 oC and controlling their growth kinetics follows different reaction times from 1 minute to 180 minutes. Base on their optical properties and estimated size to track their growth kinetics follow the Lamer model. Structure and morphology characterized were investigated by XRD pattern and transmission electron microscopy (TEM). All samples show cubic zinc blende type structures. The average NCs size can be calculated by absorption spectra, XRD and TEM, these results lie in close vicinity with each other. The energies of photoluminescence (PL) peaks and band gap of CdSe NCs can be tuned within the regions of 1.99 eV to 2.13 eV and 1.92 eV to 2.12 eV with increasing reaction time. The Stokes shifts and PL emission peaks are narrow, thus confirming the formation of uniformly distributed NCs.

Metallogenic discrimination by sphalerite trace element geochemistry: An example from the Fengyan Zn-Pb deposit in central Fujian, SE China

Central Fujian is an important polymetallic (Zn-Pb-Ag-Cu-Mo-Au) mineral province in southeastern China, yet its mineralization is still disputed with proposed genetic models ranging from Proterozoic volcanogenic massive sulfide (VMS) to Mesozoic skarn-type mineralization. The Fengyan stratabound Zn-Pb deposit is mainly hosted in marble of the Meso-Neoproterozoic Longbeixi Formation. The deposit contains two types of ore-stage sphalerite (Ⅰ and II) distinguishable based on their paragenetic relations and associated mineral assemblages. Sphalerite I generally occurs as solitary crystals characterized by black to red internal reflections. Sphalerite II is commonly associated with galena and chalcopyrite, and has yellow internal reflections. Sphalerite I has lower concentrations of Co, Cd, Cu, Pb, Ag, and Bi, but higher concentrations of Fe, Mn, and In compared to sphalerite II. Both sphalerite types have very low contents of Ga, Ge, and Sn. According to a large, global sphalerite geochemical database of well-studied VMS and skarn deposits compiled as part of this study, skarn-hosted sphalerite is characterized not only by a broader range of contained trace element contents than its VMS-hosted equivalent but also by higher concentrations of Fe, Ga, Ge, and Ag and lower Mn, Cd, In, and Co. Trace element geochemistry and metal concentrations can thus be used to distinguish VMS and skarn deposits. Overall, the two sphalerite types from Fengyan have similar trace element compositions to those of skarn-hosted (but not VMS-hosted) sphalerite. In addition, the two types of sphalerite and their coexisting minerals have a narrow in-situ δ34S range (-1.6 to 4.1 ‰, mean 2.3 ‰), indicating a magmatic source. The elemental and isotopic geochemical evidence suggests that Fengyan is best classified as a stratabound, distal Zn-Pb skarn deposit. Our work highlights the effectiveness of sphalerite trace element geochemistry for differentiating ore deposit types, thereby presenting a possible tool in support of both Zn-Pb ore exploration and research.

Study of Electronic Properties of GaAs Semiconductor Using Density Functional Theory

The properties of GaAs material in zinc blende type was calculated using Hiroshima Linear Plane Wave program based on the Density Functional Theory. This calculation aims to determine electronic properties of GaAs material are based on Density of States and energy band structure. This simulation’s results are DOS shows that hybridization of s orbital of Ga with s orbital of As provides covalent properties. The simulation of energy band structure from GaAs material indicates that semiconductor properties of GaAs is direct band gap. The energy band gap results obtained for GaAs is 0.80 eV. The computational result of the energy band gap calculation form HiLAPW has better accuracy and prediction with good agreement within reasonable acceptable errors when compared to some other DFT programs and the results of the experimental obtained.

Ore mineralogy and trace element (re)distribution at the metamorphosed Lappberget Zn-Pb-Ag-(Cu-Au) deposit, Garpenberg, Sweden

Qualitative and quantitative mineralogical and textural investigations were undertaken for the different sulfide minerals in the 1.89 Ga Lappberget deposit, with a focus on sphalerite and pyrite. Three sphalerite types were identified and associated with: (1) main massive sulfide mineralization, (2) Fe-Mn skarn ore, and (3) Ag-rich fissure veins. Sphalerite-1 contained a relatively higher amount of trace elements (Fe, Co, Ge, Cu, Sn, and Au) but is lower in Mn/Fe, Ga, and Hg compared to sphalerite-2. Evidence of tectono-metamorphic modification of sulfides is observed throughout the deposit, such as the formation of growth twins and deformation twins in sulfides, the development of high-angled triple-point junctions in recrystallized pyrite and sphalerite, and the formation of ‘ball ore’ or ‘durchbewegung’ textures within mineralized shear zones. The recrystallization of pyrite and galena may have led to the re-distribution of fluid-mobile elements (As, Cu, Zn, Pb, Ag, and Au), some of which were deposited in discordant Ag-rich fissure veins peripheral to the main massive sulfide lenses. Trace element signatures of sulfides in Lappberget are compatible with the other metamorphosed and deformed, subseafloor volcanogenic carbonate replacement (SVALS)-type deposits in the Bergslagen mining district.

Parameters of crystal and electronic structure and magnetic properties of mechanically alloyed Ni3C cubic carbide

The cubic Ni3.3C carbide has been fabricated by mechanical alloying of elemental Ni powder and the multiwalled carbon nanotubes in a high energy planetary ball mill. Crystal structure of carbide obtained belongs to the defective structure of ZnS sphalerite type according to x-ray diffraction data. Parameters of the electronic structure of Ni3.3C were calculated by linearized muffin-tin orbitals method within the plane-wave approximation using as an input the defined parameters of crystal structure. Magnetic properties, such as temperature and field dependences of the magnetic susceptibility of Ni3.3C have been studied. Based on experimental data obtained by studying the crystal structure and magnetic properties of Ni3.3C, as well as on the basis of calculations of electronic structure parameters, a preferred displacement of the carbon atoms in tetrahedral voids of Ni crystal lattice has revealed.

Greener synthesis and characterization of cadmium-tellurium quantum dots using aqueous extract of waste orange peel

Cadmium-Tellurium quantum dots are inorganic semiconductor material. In the present study, highly stable Cadmium-Tellurium (CdTe) quantum dots with good optical properties were successfully synthesized by using waste orange peel extract. Fourier-transform infrared spectroscopy (FTIR) identified the presence of hydroxyl, carboxyl and amine groups. Multifunctional X-ray Photoelectron Spectroscopy (XPS) confirmed the presence of cadmium and tellurium. The average size of the quantum dots was found to be 6nm using Transmission Electron Microscopy (TEM). The cubic zinc blende type crystalline structure of quantum dots was confirmed by X-ray powder diffraction (XRD). Thermal stability was studied using thermo-gravimetric analysis (TGA). The influence of temperature with respect to mass change of 8% was observed at 200C. The high luminescence property exhibits at the wavelength of 502 nm were investigated using photoluminescence analysis (PL) and the blue shift is confirmed by UV-Visible spectroscopy.

First-principles investigations of electronic structures and optical spectra of wurtzite and sphalerite types of ZnO1-xSx (x=0, 0.25, 0.50, 0.75 &1) alloys

Alloying of the zinc oxide (ZnO) with sulfur (S) chalcogen reveals vivid modifications of its electronic and optical properties driven by the dramatic restructuring of electronic structure. Here, we systematically executed mutual alloying of ZnO and ZnS in two different structural phases namely the wurtzite and sphalerite phases. Evolution in the physical properties of the designed ZnO1-xSx alloys for the compositions, x = 0, 0.25, 0.50, 0.75 and 1 has been comprehensively examined by using full-potential linearized augmented-plane-wave plus local orbital approach within density functional theory. It is observed that the replacement of the Oxygen by Sulfur atoms significantly affects the band-structure profiles of ZnO1-xSx alloys in both wurtzite and sphalerite geometries. Furthermore, by increasing the S contents in ZnO1-xSx alloys, the conduction band minimum is found to be moved in the upward direction resulting in enhancement of the bandgaps. The electronic bandgaps of ZnO1-xSx alloys were enhanced from 2.65 eV to 3.68 eV in wurtzite and from 2.50 eV to 3.60 eV in sphalerite phase. Similarly, the imaginary parts of the dielectric function of ZnO1-xSx move towards a high energy regime with an increase in S composition, which resulted in a blueshift in their absorption edges. Our results are found well-matching with available theoretical and experimental results. The variation in the energy bandgaps and optical properties makes the S-rich ZnO a promising candidate for ultraviolet photoelectronic devices.

Synthesis and structural investigation of stoichiometric iron mononitride thin films

We report the synthesis of iron mononitride (FeN) thin films having zinc blende (ZB) type structure, deposited using a direct current magnetron sputtering process on amorphous quartz substrates. The effect of substrate temperature (Ts) on the structure of FeN thin films was systematically investigated by varying the Tsfrom 300 to 500 K(in close intervals of 25K). The long-range as well as the local structure of samples was studied using x-ray diffraction (XRD), x-ray absorption near edge spectroscopy (XANES) at N K-edge, Fe L and K-edge and extended x-ray absorption fine structure (EXAFS) at Fe K-edge. The lattice parameter (LP) obtained from XRD and the presence of an intense pre-edge feature in Fe K-edge XANES confirms the ZB-structure of FeN samples. It was found in this work that the stoichiometric FeN with a LP close to its theoretical value can only be obtained in a narrow temperature regime due to minimization of stresses generated during the growth near the thermodynamic equilibrium conditions. These findings were further validated by EXAFS results yielding Fe–N and Fe–Fe bond distances, in conformity with the theoretically predicted values for FeN in ZB type structure.

Hexagonal iron nitride monolayer on Cu(001): Zigzag-line-in-trough alignment

Strong interaction between metal atoms and adsorbates sometimes leads to the formation of surface compounds. In such cases, the registry with a metal substrate plays a key role in determining the overlayer stability. In this paper, we present a structural model for a hexagonal Fe-N monolayer grown on a square Cu(001) substrate. The system exhibits a stripe pattern composed of dark (1 × 1) stripes (A-stripes) and bright (3×3) stripes (B-stripes). We suppose the FeN stoichiometry and the structure similar to a single (111) layer of zincblende type γ″-FeN. Based on protrusion alignment observed by scanning tunneling microscopy (STM), we propose that the A-stripe has a relaxed hexagonal lattice composed of equilateral Fe triangles with N atoms at the center whereas the B-stripe has a uniaxially-compressed lattice composed of isosceles Fe triangles. Connection of these two lattice with small inclination produces zigzag Fe-atom rows embedded in [110] troughs on the Cu(001) substrate. Thus, the FeN overlayer is commensurate with Cu(001) along the [1¯10] direction. The (3×3) reconstruction in B-stripes effectively relieves the compressive stress. Our model shows the way in which a stable overlayer exists on the substrate of different symmetry and lattice constants by forming a stripe pattern.

Second-harmonic generation in zinc blende crystals under combined action of femtosecond optical and strong terahertz fields

The influence of a short intense (with an electric field strength up to 250 kV cm−1) terahertz (THz) pulse on the generation of second harmonic (SH) of Ti : sapphire laser radiation in crystals of zinc blende type (InAs and GaAs), characterised by nonzero bulk quadratic susceptibility, is investigated. It is experimentally shown for InAs(100) that, in the case of s-polarised first and second harmonics, an application of s-polarised THz field changes significantly the SH signal. The THz field-induced azimuthal dependence of the SH signal is in good agreement with the results of theoretical calculation within a phenomenological approach. The dependence of the SH signal on the delay time between the optical and THz pulses is investigated. This dependence for the GaAs crystal repeats the envelope of the THz pulse intensity, whereas in the case of InAs crystal there is a significant discrepancy, caused by the nonlinear dynamics of strong THz field in InAs.