The structural and electrical properties of liquid copper selenide

Barnes, Adrian C; Enderby, J. E.

doi:10.1080/13642818808208461

Cited by 25 publications

(27 citation statements)

References 23 publications

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“…It is worth noting that chalcogen pairing has been observed by diffraction experiment in some equiatomic liquid mixtures, e.g. CuSe 71 and KTe 72 . The conductivity of ℓ-Cu-Se has been measured over a range of composition and behaves in a similar way to that found in our simulations, showing a strong minimum at the composition Cu 2 Se and then passing through a maximum in the region of CuSe before falling to the low values associated with ℓ-Se.…”

Section: Atomic Ordering and Electronic Propertiesmentioning

confidence: 90%

Structure, dynamics, and electronic structure of liquid Ag-Se alloys investigated byab initiosimulation

1996

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Ab initio molecular-dynamics simulations have been used to investigate the structure, dynamics and electronic properties of the liquid alloy Ag1−xSex at 1350 K and at the three compositions x = 0.33, 0.42 and 0.65. To provide a point of reference, calculations are also presented for the equilibrium structure and the electronic structure of the α-Ag2Se crystal. The calculations are based on density-functional theory in the local density approximation and on the pseudopotential plane-wave method. For the solid, we find excellent agreement with experiment for the equilibrium lattice parameters and the atomic coordinates of the 12-atom orthorhombic unit cell, and we present an analysis of the electronic density of states and density distribution. The reliability of the liquid simulations is confirmed by detailed comparisons with very recent neutron diffraction results for the partial structure factors and radial distribution functions (RDF) of the stoichiometric liquid Ag2Se. Comparison with the predictions of an empirical interaction model due to Rino et al. is also given for ℓ-Ag2Se. The ab initio simulations show a dramatic change of the Se-Se RDF with increasing Se content. This change is due to the formation of Se clusters bound by covalent bonds, the Se-Se bond length being almost the same as in pure c-Se and ℓ-Se. The clusters are predominantly chain-like, but for higher x there is a significant fraction of 3-fold coordinated Se atoms. It is shown that the equilibrium fractions of Se present as isolated atoms and in clusters can be understood on a simple charge-balance model based on an ionic interpretation. The Ag diffusion coefficient in the simulated stoichiometric liquid is consistent with experimental values measured in the hightemperature superionic solid. The Ag and Se diffusion coefficients both increase with Se content, in spite of the Se clustering. An analysis of the Se-Se bond dynamics reveals surprisingly short bond lifetimes of less than 1 ps. The electronic density of states (DOS) for ℓ-Ag2Se strongly resembles that of the solid. Some of the changes of DOS with composition arise directly from the formation of Se-Se covalent bonds. Results for the electronic conductivity σ obtained using the Kubo-Greenwood approximation are in adequate agreement with experiment for ℓ-Ag2Se, but for the high Se contents the simulation results for σ are 3-4 times greater than experimental values. Possible reasons for this are discussed.

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Section: Atomic Ordering and Electronic Propertiesmentioning

confidence: 90%

Structure, dynamics, and electronic structure of liquid Ag-Se alloys investigated byab initiosimulation

1996

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“…2(b)] shows that there is again a first Te-Te coordination peak at 2.8 A, having in this case a coordination of 0.96. This virtually complete pairing of tellurium atoms is in sharp contrast to the heterocoordination of liquid CuTe and the partial pairing of selenium in liquid CuSe (Se-Se coordination of -0.6) [20]. It is informative to compare this liquid structure with that of crystalline KTe [13,14], whose peaks are indicated in the figure by the vertical bars with heights determined by the coordination number weighted by the appropriate prefactors from Eq.…”

Section: S-mentioning

confidence: 96%

Charge transfer in liquid semiconductors: The K-Te system

1992

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The neutron diffraction patterns of molten K x Tei-x alloys for x=0.12 and x=0.50 demonstrate the persistence of covalently bonded tellurium in the liquid. In the case of liquid Ko.12Teo.88, the measured structure is dominated by the Te-Te contribution, and is remarkably similar to that of pure liquid tellurium. The equiatomic alloy Ko.50Teo.50 is shown to contain mostly Te pairs which are identified with Zintl ions, Te2 2~. The presence of these ions explains the semiconducting behavior of these alloys deduced from recent electrical transport measurements.PACS numbers: 72.80.PhThe chalcogen elements S, Se, and Te play a principal role in the formation of liquid semiconducting matter [1,2]. The nature of the chemical bonding in these elements, namely, their tendency to form twofold covalent bonds in the melt, appears to be central to the semiconducting behavior of their melts and many of their alloys. Of these, tellurium is perhaps the least understood. Pure liquid (/-) Te is a semimetal, whose conductivity places it between the regimes of Ziman scattering theory (metallic) and diffusive (semiconducting) behavior. Possible ambipolar conduction has made transport [3] and optical [4,5] properties of /-Te difficult to interpret in a consistent manner. Further confusion arises from diffraction measurements, where the measured radial distribution function (RDF) shows that there is no well-defined first coordination shell [1,6], leaving open the fundamental point of whether the number of bonded neighbors is two or three. This is in contrast to liquid selenium, where a well-defined first coordination peak with an area of two atoms is derived from neutron diffraction results [7].The peculiar structure of pure /-Te has been explained by Cutler [2] as containing a high density of singlebonded (IF or D~) and threefold-bonded (3F or D + ) defects in a nominally twofold network. Later on, Silva and Cutler [5] proposed that the electronic and optical properties may be explained if one assumes very short (three to four atoms) covalently bonded, electrostatically interacting chains with a nearly equal density of IF and 3F sites. Thus, the first peak in the RDF of pure /-Te has contributions from long-lived twofold (intrachain) and short-lived 3F (interchain) and IF (dangling bond or chain termination) sites. The 3F and IF sites are in "fast exchange" as short chains interact, a process that results in the observed broad, asymmetric first RDF peak. This view is consistent with the rapid transition from semimetallic to semiconducting behavior observed when alloying Te with Se [3], Tl [1], or K [8]. Magafia and Lannin [4] have also suggested that threefold bonding is needed to explain the Raman spectra of pure /-Te, and their observation of a sudden qualitative change in the Raman spectra of the Se-Te system at ~20-30 at.% Se was interpreted as a transition from threefold to twofold bonding. These authors preferred a modified version of an earlier model of Cabane and Friedel [9], in which the structure of pure /-Te is a continuou...

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“…The lower reflection level (S11 ≤ -10 dB) is observed in the region of 28 GHz to 28.85 GHz. The metasurface is clearly shown the switching between transmission and reflection at different resonators with different bandwidths [17].…”

Section: Resultsmentioning

confidence: 97%

Design of Reconfigurable Micro fluidic Met surface with Different Semiconductor Alloys

Al‐Ghamdi

Yousaf

Yahyaoui

et al. 2021

ijmcr

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In this work, design of a reconfigurable metasurface using all-dielectric materials is presented. An elliptical all-dielectric microfluidic-based metasurface is designed using Rogers RO3210 substrate (ε = 10.2 and tan δ = 0.03). The substrate is covered with microfluidic channel which is filled with five various AgTiTe2, Cu2S, Te.5 Se.5, CuTSe2 and Cu3SbSe4. semiconductor alloys. The reflection and transmission characteristics of the designed metasurface are analyzed in the frequency range of 20-30 GHz using COMSOL Multiphysics software. The results demonstrate that change in the semiconductor alloy in the microfluidic channel various the dynamic transmission and reflection characteristics of the metasurface and thus depicts a reconfigurable operation of the proposed design.

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The structural and electrical properties of liquid copper selenide

Cited by 25 publications

References 23 publications

Structure, dynamics, and electronic structure of liquid Ag-Se alloys investigated byab initiosimulation

Structure, dynamics, and electronic structure of liquid Ag-Se alloys investigated byab initiosimulation

Charge transfer in liquid semiconductors: The K-Te system

Design of Reconfigurable Micro fluidic Met surface with Different Semiconductor Alloys

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