Simulations Of Cu Research Articles

Ordering/displacive ferrielectricity in 2D CuInP2S6

Using DFT-based molecular dynamics simulation of Cu+ cations flipping and In3+ cations displacive dynamics, we clarify the dipole ordering of CuInP2S6 ferrielectrics through the second order Jahn-Teller effect which determines the double-well potential for copper cations as well as three-well potential for indium cations inside the structural layers. The temperature dependence of the spatial distribution of Cu+ and In3+ cations is also described within the quantum anharmonic oscillator model. In3+ cations play a decisive role in the character of the polar ordering: at ambient or for positive pressures, the first order transition occurs; with the rise of negative compression, the ferrielectric transition evolves to the second order. The peculiarities of spontaneous polarization switching are related to the contributions of copper and indium cationic sublattices.

Design and simulation of Cu2SnSe3-based solar cells using various hole transport layer (HTL) for performance efficiency above 32%

Abstract The current research investigates the (Ni/V2O5/Cu2SnSe3/In2S3/ITO/Al) novel heterostructure of Cu2SnSe3-based solar cell numerically using the SCAPS-1D simulator. The goal of this study is to determine how the proposed cell’s performance will be impacted by the V2O5 hole transport layer and the In2S3 electron transport layer. To enhance cell performances, the effects of thickness, carrier concentration and defect in the absorber layer, electron concentration, hole concentration, total generation and recombination, interface defect, J-V and Q-E characteristics, and operating temperature are investigated. Our preliminary simulation results demonstrate that, in the absence of V2O5 HTL, the efficiency of a conventional Cu2SnSe3 cell is 22.14%, a value that is in suitable agreement with the published experimental values. However, a simulated efficiency of up to 32.34% can be attained by using the HTL and ETL combination of V2O5 and In2S3, respectively, and optimized device parameters. The ideal carrier concentration and layer thickness for the Cu2SnSe3 absorber layer are, 1018 cm−3 and 1000 nm, respectively,. However, it is also seen that for optimum device performances, the back-contact metal work function (BMWF) must be higher than 5.22 eV. The outcomes of this contribution may open up useful research directions for the thin-film photovoltaic sector, enabling the production of high-efficient and low-cost Cu2SnSe3-based PV cells.

Molecular simulation of Cu, Ag, and Au-decorated Molybdenum doped graphene nanoflakes as biosensor for carmustine, an anticancer drug

This study delves into the fascinating realm of molybdenum-doped graphene ([email protected]) complexes, featuring captivating adsorption sites for oxygen (O) and chlorine (Cl), adorned with the mesmerizing presence of silver (Ag), gold (Au), and copper (Cu). These alluring metal-doped compounds have been proposed as potential biosensor materials, with a particular focus on their prowess in the adsorption of carmustine (cmt). Employing the formidable density functional theory (DFT) at the B3LYP-GD3BJ/def2-SVP computational approach. Enveloped by the intrigue of two distinct adsorption sites—O and Cl—we stumbled upon a remarkable revelation. Among the contenders, [email protected][email protected] emerged triumphant with the lowest energy gap at the Cl site of carmustine adsorption, an astonishingly meager value of 0.082 eV. Following closely behind, [email protected][email protected] boasted a respectable energy gap of 0.852 eV. However, [email protected][email protected] and [email protected]@GP took the stage with their grandiose energy gaps, exhibiting values of 1.128 eV and 1.843 eV, respectively. Substantially, the captivating saga unfolds, presenting the distribution of adsorption energies as follows: [email protected]@GP > [email protected]@GP > [email protected][email protected] > [email protected][email protected] > [email protected][email protected] > [email protected][email protected] In a captivating interplay of energies, the system [email protected] unveils its preferences: the O site reigns supreme with an Eads of -0.59 eV, while the Cl site humbly follows with an Eads of -0.03. Meanwhile, within the realm of the [email protected] system, the Chlorine site claims dominance, boasting an Eads of -1.30eV, while the Oxygen site asserts its presence with an Eads of -0.21 eV. As for the [email protected] system, the Chlorine site emerges as the epitome of favorability, commanding an Eads of -0.83 eV, while the Oxygen site modestly exhibits an Eads of -0.29 eV. Through meticulous exploration, the results unequivocally demonstrate the remarkable qualities of the investigated complexes, positioning them as promising nanomaterials for the realm of drug delivery.

Molecular simulation of Cu, Ag, and Au-decorated Si-doped graphene quantum dots (Si@QD) nanostructured as sensors for SO2 trapping

In view of the numerous environmental hazards and health challenges linked to sulfur (iv) oxide (SO2), an indirect greenhouse gas, and the resultant need to develop efficient gas nanosensor devices, this research had as its principal focus on the theoretical evaluation of the gas sensing potential of metals: Ag, Au and Cu functionalized silicon-doped quantum dots (Si@QD) for the detection and adsorption of SO2 gas investigated using the first-principles density functional theory (DFT) computation at the B3LYP-D3(BJ)/def2-SVP level of theory. Eight (8) possible adsorption modes: SO2_O_Si@QD, SO2_O_Ag_Si@QD, SO2_O_Au_Si@QD, SO2_O_Cu_Si@QD, SO2_S_Si@QD, SO2_S_Ag_Si@QD, SO2_S_Au_Si@QD, and SO2_S_Cu_Si@QD were considered based on SO2 interactions with the studied materials at the -S and -O sites of the SO2 molecule. The counterpoise correction (BSSE) showed that five of the eight interactions had favorable Ead + BSSE values ranging from −0.31 to −1.98 eV. All the eight interactions were observed to be thermodynamically favorable with ΔG and ΔH ranging from −129.01 to −200.24 kcal/mol and −158.26 to −229.73 kcal/mol respectively. Results from the topology analysis reveal that van der Waals forces occurred the greatest at the gas-sensor interphase while SO2_S_ Cu_Si@QD is predicted to have the highest sensing potency based on the conductivity and recovery time estimations. These results confirm the potential efficient feasibility of real-world device application of the metals (Ag, Au, Cu) functionalized Si-doped QDs.

Computer simulation of Cu: AlOOH/water in a microchannel heat sink using a porous media technique and solved by numerical analysis AGM and FEM

Extensive improvements in small-scale thermal systems in electronic circuits, automotive industries, and microcomputers conduct the study of microsystems as essential. Flow and thermic field characteristics of the coherent nanofluid-guided microchannel heat sink are described in this perusal. The porous media approximate was used to search the heat distribution in the expanded sheet and Cu: γ - AlOOH/water. A hybrid blend of Boehme copper and aluminum nanoparticles is evaluated to have a cooling effect on the microchannel heat sink. By using Akbari Ganji and finite element methods, linear and non-linear differential equations as well as simple dimensionless equations have been analyzed. The purpose of this study is to investigate the fluid and thermal parameters of copper hybrid solution added to water, such as Nusselt number and Darcy number so that we can reach the best cooling of the fluid. Also, by installing a piece of fin on the wall of the heat sink, the coefficient of conductive heat transfer and displacement heat transfer with the surrounding air fluid increases, and the efficiency of the system increases. The overall results show that expanding values on the NP (series heat transfer fluid system maximizes performance with temperatures) volume division of copper, as well as boehmite alumina particles, lead to a decrease within the stream velocity of the Cu: AlOOH/water. Increasing the volume fraction of nanoparticles in the hybrid mixture decreases the temperature of the solid surface and the hybrid nanofluid. The Brownian movement improves as the volume percentage of nanoparticles in the hybrid mixture grows, spreading the heat across the environment. As a result, heat transmission rates rise. As the Darcy number increases, the thermal field for solid sections and Cu: AlOOH/water improves.

Can’t we negotiate the importance of electron correlation? HF vs RIMP2 in ab initio quantum mechanical charge field molecular dynamics simulations of Cu+ in pure liquid ammonia

The impact of electron correlation in quantum mechanical charge field molecular dynamics (QMCF MD) simulations of Cu+ in pure liquid ammonia has been investigated by comparing the results obtained at the Hartree–Fock (HF) level and via resolution-of-identity second order Møller–Plesset perturbation theory (RIMP2). To achieve a manageable computational demand, a rigid-body solvent model was employed to describe the NH3 molecules. The solvation structures observed in both cases have similar characteristics in which tetrahedral [Cu(NH3)4]+ dominates with average CuN distances of 2.24 (HF) and 2.12 (RIMP2) Å, respectively. The ligand dynamics in the first solvation shell of the RIMP2 simulation are notably higher than in the HF case and resulted in the formation of an intermediate [Cu(NH3)3]+ complex along the sampling period. Electron correlation effects were found to mainly impact the solvent–solvent hydrogen bonding interaction, thereby providing a more accurate description of the structural properties in terms of the average CuN distances along with greatly enhanced ligand exchange dynamics occurring between the first and second solvation shell.

Effectively one-dimensional phase diagram of CuZr liquids and glasses

This paper presents computer simulations of Cu$_x$Zr$_{100-x}$ $(x=36,50,64)$ in the liquid and glass phases. The simulations are based on the effective-medium theory (EMT) potentials. We find good invariance of both structure and dynamics in reduced units along the isomorphs of the systems. The state points studied involve a density variation of almost a factor of two and temperatures going from 1500 K to above 4000 K for the liquids and from 500 K to above 1500 K for the glasses. For comparison, results are presented also for similar temperature variations along isochores, showing little invariance. In general for a binary system the phase diagram has three axes: composition, temperature and pressure (or density). When isomorphs are present, there are effectively only two axes, and for a fixed composition just one. We conclude that the liquid and glass parts of the thermodynamic phase diagram of this metallic glass former at a fixed composition is effectively one-dimensional in the sense that many physical properties are invariant along the same curves, implying that in order to investigate the phase diagram, it is only necessary to go across these curves.

Clarifying the definition of ‘transonic’ screw dislocations

ABSTRACT A number of recent Molecular Dynamics (MD) simulations have demonstrated that screw dislocations in face centred cubic (fcc) metals can achieve stable steady state motion above the lowest shear wave speed () which is parallel to their direction of motion (often referred to as transonic motion). This is in direct contrast to classical continuum analyses which predict a divergence in the elastic energy of the host material at a crystal geometry dependent ‘critical’ velocity . Within this work, we first demonstrate through analytic analyses that the elastic energy of the host material diverges at a dislocation velocity () which is greater than , i.e. . We argue that it is this latter derived velocity () which separates ‘subsonic’ and ‘supersonic’ regimes of dislocation motion in the analytic solution. In addition to our analyses, we also present a comprehensive suite of MD simulation results of steady state screw dislocation motion for a range of stresses and several cubic metals at both cryogenic and room temperatures. At room temperature, both our independent MD simulations and the earlier works find stable screw dislocation motion only below our derived . Nonetheless, in real-world polycrystalline materials cannot be interpreted as a hard limit for subsonic dislocation motion. In fact, at very low temperatures our MD simulations of Cu at 10 Kelvin confirm a recent claim in the literature that true ‘supersonic’ screw dislocations with dislocation velocities are possible at very low temperatures.

Applied research on the numerical simulation of Cu and Cd transport laws in a metal mining area

China is paying increasing attention to the ecological environment, and heavy metal pollutants produced during mining and smelting in metal mines have caused serious environmental problems to the soil in mining areas. Heavy metal pollution by Cd and Cu in the soil of a metal mining area in Leiyang City, Hunan Province, China, is used here as an example. The total content of heavy metals and the contents of various forms were determined. High Cd and Cu contents were found, and the main forms of the two heavy metals were in the residual state. Then, using the COMSOL software, the migration and evolution of Cu and Cd in the soil were predicted by real simulations. On this basis, a soil management plan was explored. The migration model shows that within 30 days, the pollutant concentration gradually decreases with increasing depth, and most of the heavy metals are concentrated in the surface layer of the soil; after migration, Cd and Cu have different concentrations at various depth levels in the soil. Among them, the soil concentration is the highest in the range of 0 cm–10 cm depth. As the depth reaches 30 cm, the concentration gradually stabilizes. The conclusions of the study provide a scientific basis for the rational use and ecological restoration of mining areas and the prevention and control of soil pollution in mining areas.

Multireaction Modeling of Lead (Pb) and Copper (Cu) Sorption/Desorption Kinetics in Different Soils

Batch kinetic experiments were carried out to quantify and describe the sorption/desorption of Cu and Pb in ten soils that exhibited a wide range of properties. Sorption isotherms were quantified using the Langmuir equation, whereas modeling of sorption/desorption kinetics was described using multireaction model (MRM). Results revealed the nonlinear sorption behavior of Cu and Pb in all soils. The ten soils exhibited higher affinity to Pb (6.4 to 36.5 mmol kg−1) in comparison to Cu (3.6 to 22.4 mmol kg−1). Simulation of Cu and Pb kinetic data indicated that the rate of sorption reaction was two orders of magnitude higher than the rate of release. Considering one irreversible site in addition to one-reversible kinetic site improved the estimation of rates of reaction for both Cu and Pb in acidic and alkaline soils. All soils exhibited sorption/desorption hysteresis where Pb-releases ranged between <0.2% and 14.4% of the total sorbed. The respective Cu releases ranged from <0.85% and 23.4%. The multireaction model, which was successful in describing Cu and Pb for all ten soils, provided insight into the processes of sorption/desorption of Cu and Pb in all soils.

Molecular dynamics simulation on the effect of transition metal binding to the N-terminal fragment of amyloid-β

We report molecular dynamics simulations of three possible adducts of Fe(II) to the N-terminal 1–16 fragments of the amyloid-β peptide, along with analogous simulations of Cu(II) and Zn(II) adducts. We find that multiple simulations from different starting points reach pseudo-equilibration within 100–300 ns, leading to over 900 ns of equilibrated trajectory data for each system. The specifics of the coordination modes for Fe(II) have only a weak effect on peptide secondary and tertiary structures, and we therefore compare one of these with analogous models of Cu(II) and Zn(II) complexes. All share broadly similar structural features, with mixture of coil, turn and bend in the N-terminal region and helical structure for residues 11–16. Within this overall pattern, subtle effects due to changes in metal are evident: Fe(II) complexes are more compact and are more likely to occupy bridge and ribbon regions of Ramachandran maps, while Cu(II) coordination leads to greater occupancy of the poly-proline region. Analysis of representative clusters in terms of molecular mechanics energy and atoms-in-molecules properties indicates similarity of four-coordinate Cu and Zn complexes, compared to five-coordinate Fe complex that exhibits lower stability and weaker metal–ligand bonding.Communicated by Ramaswamy H. Sarma

Copper-Chalcogen Bonds in Olfaction: Accurate ab Initio Characterization of CuSH and CuOH.

From highly correlated ab initio methods at the CCSD(T) level, with and without the inclusion of scalar relativistic effects, accurate 3D potential energy surfaces (PESs) of CuSH and CuOH were generated in their electronic ground state. The PESs are incorporated into perturbative and variational treatments of nuclear motions. Using these approaches, we derived a set of accurate spectroscopic parameters and the pattern of the vibrational states of CuXH (X = O,S) up to 4000 cm-1. The applied calculations at the CCSD(T)/aug-cc-pV5Z-DK level of theory are validated using several experimental high-resolution spectroscopy data (including rotational spectroscopy) available in the literature. The optimized equilibrium geometries of CuSH and CuOH with bending angles of 93.9° and 110.2°, Cu-X bond lengths of 2.088 and 1.764 Å, and X-H bond lengths of 1.344 and 0.961 Å, respectively, accurately reproduce the experimental structures and clearly show the importance of the scalar relativistic effects. The anharmonic frequencies, ν1, ν2, and ν3, are computed at 3655.5, 746.3, and 623.3 cm-1 for CuOH and at 2572.9, 588.9, and 396.6 cm-1 for CuSH, respectively. Finally, the PESs are derived as anharmonic force fields for CuXH (X = O, S) that can be incorporated into large scale molecular dynamics simulations of Cu-X containing compounds. The results are discussed within the scope of available literature on the effects of substitution of oxygen by sulfur for putative molecular recognition mechanisms.

Kinetics simulation of Cu and Cd removal and the microbial community adaptation in a periphytic biofilm reactor

Periphytic biofilm reactor (PBfR) shows great potential in pollutants removal. However, few studies were focused on mathematical model of pollutants removal in PBfR. A three-step PBfR was designed and a new model was developed to simulate the kinetics of Cu and Cd removal from simulated wastewater. The results show that the PBfR could remove 99.0% Cu and 99.7% Cd from liquid wastewater. The experiment data could be well fitted with a high correlation coefficients both for Cu and Cd. The microbial community in the PBfR could be self-adjusted to tolerate the toxicities of Cu and Cd, resulting in sustainable and high decontamination efficiencies. The eukaryote in the PBfR played a vital role in Cu and Cd removal. The prokaryote showed negative effect on Cu and Cd removal, though it had more diversity than eukaryote. This study provides a new approach for Cu and Cd removal and their kinetics simulation in photoautotrophic bioreactor.

Device simulation of Cu(In,Ga)Se2 solar cells by means of voltage dependent admittance spectroscopy

The simulation of solar cell devices is important for the understanding of defect physics and loss mechanisms in real solar cells. On the other hand, voltage dependent admittance spectroscopy delivers essential information for establishing a baseline simulation model of Cu(In,Ga)Se2 (CIGSe) solar cells. Here we give an explanation for the weak temperature dependence of the N1-signal, the latter being not compatible with a bulk defect or with a simple hole barrier at the Mo back contact. Furthermore, we find a Ed,IF – EV ≈ 0.3 eV deep recombination-active acceptor state at the absorber/buffer interface made of air-light exposed CIGSe absorbers. This gives us the ability to explain the reduction of power conversion efficiency of solar cells made from air-light exposed absorbers. From the voltage dependent capacitance step of this interface defect we can deduce the formerly unknown position of the Fermi level at the hetero junction in equilibrium which is close to mid-gap. Simulation of dark J-V curves allows a refinement of the parameter of this absorber/buffer interface defect, resulting in a defect density of Nd,IF ≈ 3.5·1011 cm−2 as well as capture cross sections of σn ≈ 4·10−16 cm2 for electrons and σp ≈ 3·10−11 cm2 for holes.

Refractive indices of layers and optical simulations of Cu(In,Ga)Se2 solar cells

Cu(In,Ga)Se2-based solar cells have reached efficiencies close to 23%. Further knowledge-driven improvements require accurate determination of the material properties. Here, we present refractive indices for all layers in Cu(In,Ga)Se2 solar cells with high efficiency. The optical bandgap of Cu(In,Ga)Se2 does not depend on the Cu content in the explored composition range, while the absorption coefficient value is primarily determined by the Cu content. An expression for the absorption spectrum is proposed, with Ga and Cu compositions as parameters. This set of parameters allows accurate device simulations to understand remaining absorption and carrier collection losses and develop strategies to improve performances.

New mononuclear copper(II) complexes from β-diketone and β-keto ester N-donor heterocyclic ligands: structure, bioactivity, and molecular simulation studies

Four new mononuclear copper(II) complexes with methyl acetoacetate and benzoylacetone in the presence of 1,10-phenanthroline and 2,2′-bipyridine were synthesized and characterized by elemental analyses, FT-IR, and UV–Vis spectroscopy. The molecular structures of complexes [Cu(MAA)(bpy)(ClO4)] (1a), [Cu(bzac)(bpy)]ClO4 (2a), [Cu(MAA)(phen)(ClO4)] (1b) and [Cu(bzac)(phen)(ClO4)] (2b) were determined by single crystal X-ray diffraction technique. 1a, 1b, and 2b are five coordinate with a distorted square pyramidal geometry and the structure of 2a consists of isolated [Cu(bzac)(bpy)]+ cations and perchlorate counter anions. The electrochemical studies of copper complexes in acetonitrile solution showed that CuII/CuI reduction processes are electrochemically irreversible. Cytotoxic activity of complexes was screened, including an MTT assay against gastric cancer cell line (MKN-45). The four Cu(II) complexes exhibited lethal effects against MKN-45 cell lines and the half maximal inhibitory concentration (IC50) values obtained were much lower in comparison with 5-fluorouracil. In addition, MTT and migration studies revealed that benzoylacetone complexes are more active than complexes of methyl acetoacetate against the MKN-45 cancer cell lines. Docking simulations of Cu(II) complexes on DNA revealed that the most stable adducts with DNA bind in the minor groove. All complexes display a binding specificity to the A/T rich regions.

Monte Carlo simulation of Cu, Ni and Fe grade determination in borehole by PGNAA technique

A prompt gamma neutron activation analysis borehole logging method for copper, nickel and iron grade estimation is proposed. The performance of the method was simulated by MCNP5 code. Based on the theory of neutron–gamma distribution on the borehole condition, the BGO scintillator and 3He neutron tube are adopted to record gamma ray spectrum and thermal neutron simultaneously, and least square method is used for the characteristic gamma ray counts calculation in the high energy range. The results of detection limit of metal grade in borehole condition indicate that the effectiveness of this logging method.

Performance prediction of chalcopyrite-based dual-junction tandem solar cells

Abstract In this work, we present SCAPS-1D simulations of Cu(In,Ga)Se2-based dual-junction tandem cells. The purpose of this work is to assess the device performances of the Cu(In,Ga)Se2-based tandem cells based on the fact that each subcell is simulated to yield a reported best efficiency at its bandgap. A method to build the J-V characteristics of tandem cells from individual J-V curves of subcells is also discussed. By thinning the absorber thickness of the top subcell, the current matching points among various bandgap combinations are examined. In spite of neither optical nor electrical loss between the top and bottom subcells, the device performances of the tandem devices do not substantially surpass the device performances of single-junction devices, which is ascribable to the relatively poor efficiencies of the wide-bandgap top subcells. We also discuss how further improvements in the wide-bandgap top subcells are needed to create a validity for making an effortful multi-junction device.

Evolution of dislocation mechanisms in single-crystal Cu under shock loading in different directions

Even though there are numerous experiments and molecular dynamic simulations of Cu under shock loading, there appears to be no literature on the evolution of different types of dislocation mechanisms and their mutual interactions during the process of shock loading, which this article addresses through molecular dynamic simulations using the Mishin EAM potential for Cu. Three different directions , , and that have been considered in this article are subjected to shock compression with piston velocities ranging between 0.3–3 km s−1. The evolution of Hirth locks, Lomer–Cottrell locks, cross-slips, jogs, and dislocation-originated stacking-fault tetrahedra are demonstrated in this article for different direction shock loading of single-crystal Cu.

Covellite CuS as a matrix for “invisible” gold: X-ray spectroscopic study of the chemical state of Cu and Au in synthetic minerals

Geological processes leading to formation of sulfide ores often result in precipitation of gold-bearing sulfides which can contain high concentrations of this metal in “invisible” (or “refractory”) state. Covellite (CuS) is ubiquitous mineral in many types of the ore deposits, and numerous studies of the natural ores show that covellite can contain high concentrations of Au. At the same time, Au-bearing covellite withstands cooling in contrast to other minerals of the Cu–Fe–S system (chalcocite, bornite, chalcopyrite), where Au exsolves at low temperatures. This makes covellite a convenient model system for investigation of the chemical state (local environment and valence) of the “invisible” Au in copper-sulfide ores (copper-porphyry, epithermal, volcanogenic massive sulfide, SEDEX deposits). Therefore, it is necessary to determine the location of Au in the covellite matrix as it will have important implications for the methods employed by mineral processing industry to extract Au from sulfide ores. Here we investigate the chemical state of Cu and Au in synthetic covellite containing up to 0.3wt.% of Au in the “invisible” state. The covellite crystals were synthesized by hydrothermal and salt flux methods. Formation of the chemically bound Au is indicated by strong dependence of the concentration of Au in covellite on the sulfur fugacity in the experimental system (d(log C(Au))/d(log f(S2))∼0.65). The Au concentration of covellite grows with increasing temperature from 400 to 450°C, whereas further temperature increase to 500°C has only minor effect. The synthesized minerals were studied using X-ray absorption fine structure spectroscopy (XAFS) in high energy resolution fluorescence detection (HERFD) mode. Ab initio simulations of Cu K edge XANES spectra show that the Cu oxidation state in two structural positions in covellite (tetrahedral and triangular coordination with S atoms) is identical: the total loss of electronic charge for the 3d shell is ∼0.3 for both positions of Cu. This result is confirmed by theoretical analysis of electron density performed using quantum theory of atoms in molecules (QTAIM). Modeling of the Au L3 edge EXAFS/XANES spectra showed that Au in covellite exists in the form of the isomorphous solid solution formed by substitution for Cu atoms in triangular coordination with the Me–S distance in the first coordination shell increased by 0.18Å relative to the pure CuS structure. The “formal” oxidation state of Au in covellite is +1. The Bader partial atomic charge for Au in covellite is lower than the charge of Cu (+0.2e vs. +0.5e) indicating that the degree of covalency for the Au-bearing covellite is higher than that of pure CuS. The analysis of electronic density of states shows that this structural position of Au results in strong interactions between hybridized Au s,p,d, S p, and Cu p,d orbitals. Such chemical bonding of Au to S and Cu can result in the formation of Au-bearing solid solution with other minerals in the Cu–Fe–S system.