Te Coordination Research Articles

Measuring Team Functioning During the COVID-19 Pandemic: Perspectives of Cancer Care Team Members.

In a public health crisis such as COVID-19, cancer teams face significant challenges including acute work disruptions, rapid shifts in clinical practice, and burnout. Within this context, it is crucial to explore team functioning from the perspectives of multiple stakeholders. This quantitative pilot study aimed to 1) measure perceptions of multi-stakeholders on key indicators of team functioning (Team Effectiveness, TE, and Team Relational Coordination, TRC) during COVID-19 and its transition, and 2) document whether patient perceptions of TE/TRC are significantly associated with their cancer care experiences. A descriptive design with repeated measures was used. Through convenience sampling, participants were recruited from two outpatient cancer clinics at a large university-affiliated hospital, in Montréal, Qc, Canada. Sixty-six participants (ie, 13 healthcare professionals, 40 patients, 6 informal caregivers, and 7 volunteers) completed e-measures at T1 (years 2021-2022) and n = 44 at T2 (year 2023). At T1, participants reported high perceptions of Team Effectiveness (scale 1 to 6) M = 4.47; SD = 0.7 (Mdn= 4.54; IQR: 4.06-5) and Relational Coordination (scale 1 to 5) M = 3.77; SD = 0.77 (Mdn= 3.81;IQR: 3.12-4.38) with no significant differences in perceptions across the four groups. At T2, no significant changes in TE/TRC perceptions were found. At both time points, patient perceptions of TE/TRC were significantly correlated with positive cancer care experiences (Spearman rank correlation rs ranging from 0.69 and 0.83; p < 0.01). To our knowledge, this is the first study documenting perceptions of cancer team functioning amidst the pandemic as reported by multiple stakeholders. Significant relationships between patient perceptions of TE/TRC and their cancer care experiences underscore the importance of including patients' views in team functioning processes. Future work should rely on larger sample sizes to further explore key elements of optimal team functioning.

Between defects and inclusions: The fate of tellurium in pyrite

Tellurium (Te) is a critical commodity, essential for renewable energy technologies and other high-tech applications. Most Te is currently recovered from anode slimes, i.e., waste arising from copper refining. Rising demand and the key role for the green transition make the diversification and extension of the Te supply important. However, the nature of Te incorporation into ores is still poorly understood and hinders their economic potential. Here, we investigate the distribution of Te in pyrite from a high-grade Au-Ag-Te epithermal-type ore, where pyrite is already processed for ‘invisible’ Au, to inform metallurgical extraction methods, and secure future Te supply. Current models of Te incorporation into pyrite suggest a solid-solution limit in relation to As, similar as for ‘invisible’ Au. In this study, we identified three distinct modes of Te incorporation in pyrite, which challenge previous solubility models: (1) Te solid-solution, at concentrations (up to 285 ppma) that significantly exceed the previously suggested solubility limit. (2) Nano-telluride inclusions along cracks that formed by intra-grain remobilization. (3) Crystal defects, enriched in Te through pipe diffusion hosting up to 0.5 at. % Te. Our results therefore provide new fundamental insights into the chemical and structural coordination of Te in pyrite, which may guide future efforts for its direct recovery.

Pressure-Induced Structural Transformations and Electronic Transitions in TeO2 Glass by Raman Spectroscopy.

TeO2 glass has been studied by Raman spectroscopy up to the record pressure of 70 GPa. The boson peak frequency ωb exhibits a decrease of the ∂ωb/∂P slope at 5-6 GPa and saturates above 30 GPa with a practically constant value up to 70 GPa. Experiment and theory indicate that pressures up to 20 GPa induce the transformation of single Te-O-Te bridges to double Te-O2-Te bridges, leading to a more compact structure, while Raman activity developing at higher pressures around 580 cm-1 signals the increase of Te coordination from 4- to 6-fold. Natural bond orbital analysis shows that double Te-O2-Te bridges favor the s → d transition and promote the increase of Te coordination through d2sp3 hybridization. This transition leads to the formation of TeO6 octahedra, in strict difference with crystalline TeO2 at the same pressure range, and to the development of a 3D network that freezes the medium range order.

Thermal and optical properties of binary magnesium tellurite glasses and their link to the glass structure

Binary magnesium tellurite glasses x MgO, (100-x) TeO2, studied to determine their glass forming range, structure, thermal and optical properties. Glasses were successfully synthesis in the range x = 10–45 mol%. Addition of 50 mol% of MgO leads to the appearance of the Mg3TeO6 crystalline phase. The molar volume decreases linearly with increasing MgO content. Both glass transition and crystallization temperature increase with increasing MgO content. The deduced glass stabilities show a slight maximum for x = 25 and 30mol%. Studying the structure of these glasses using Raman spectroscopy reveals the transformation of trigonal bipyramid TeO4 (tbp) structural unit to the trigonal pyramid TeO3 units with the intermediate phase TeO3+1. The coordination of Te–O decreases with increasing MgO content. The UV–Vis spectra show a shift of the UV-cutoff toward higher energy and the measured refractive index decreases with increasing MgO. Optical band gap was estimated and the obtained values were used to calculate molar refractivity, molar polarizability and a calculated refractive index. The metallization criterion is found in the range (0.399–0.417) indicating good optical nonlinearity of the prepared glasses.

A Natural 2D Heterostructure [Pb3.1Sb0.9S4][Au xTe2- x] with Large Transverse Nonsaturating Negative Magnetoresistance and High Electron Mobility.

We report the two-dimensional (2D) natural heterostructure [Pb3.1Sb0.9S4][Au xTe2- x] ( x = 0.52-0.36) which shows anomalous, transverse nonsaturating negative magnetoresistance (MR). For x = 0.52, the material has a commensurately modulated structure with alternating [Pb3.1Sb0.9S4] rocksalt layers and atomically thin [Au xTe2- x] sheets, as determined by single-crystal X-ray diffraction using a (3 + 1)-dimensional space group; for other x compositions, the modulated structure is absent and the Au and Te atoms are disordered. The transport properties in this system at low temperature (<100 K) are dominated by an unusual 2D hopping mechanism, while at room temperature a high carrier mobility of ∼1352 cm2 V-1 s-1 is obtained ( x = 0.36). The confined electrons within the [Au xTe2- x] layers are also exposed to interlayer coupling with the insulating [Pb3.1Sb0.9S4] layers, and as a result, the properties of the heterostructures emerge not only from the constituent layers but also the interactions between them. Furthermore, the various Au and Te coordination patterns found in the [Au xTe2- x] sheets as a function of x further contribute to a unique electronic structure that leads to the anomalous nonsaturating negative MR with different field dependent behaviors. First-principles calculations indicate that the [Au xTe2- x] sheets are responsible for the unusual electrical transport properties in this 2D system.

X-ray photoelectron spectra of Ge-As-Te glasses

Ternary Ge10AsxTe90-x glasses with a mean coordination number (MCN) from 2.3 to 2.8 were prepared, and their physical and structural properties were characterized. It was found that, the density of the glass decreases but glass transition temperature Tg increases, and the near infrared transmission edge shifts to shorter wavelength with increasing As content. The Ge, As, and Te 3d spectra were decomposed into different doublets that correspond to different structural units and the results showed that, the numbers of Te-Te-Te trimmers and Te-Te-As(Ge) structural units decrease and finally disappear, while the perfect AsTe3/2 pyramidal and GeTe4/2 tetrahedral structure in Te-rich samples gradually transferred to defect structures including As-As and Ge-Ge homopolar bonds with increasing As concentration. No threshold behaviour can be found in the structural evolution of Ge10AsxTe90-x glasses due to a large atomic contrast between As and Te, and no any change in the chemical coordination of Te can be observed even in Te-poor glasses.

125Te NMR Probes of Tellurium Oxide Crystals: Shielding-Structure Correlations.

The local environments around tellurium atoms in a series of tellurium oxide crystals were probed by 125Te solid-state NMR spectroscopy. Crystals with distinct TeOn units (n from 3 to 6), including Na2TeO3, α-TeO2 and γ-TeO2, Te2O(PO4)2, K3LaTe2O9, BaZnTe2O7, and CsYTe3O8 were studied. The latter four were synthesized through a solid-state process. X-ray diffraction was used to confirm the successful syntheses. The 125Te chemical shift was found to exhibit a strong linear correlation with the Te coordination number. The 125Te chemical-shift components (δ11, δ22, and δ33) of the TeO4 units were further correlated to the O-Te-O-bond angles. With the aid of 125Te NMR, it is likely that these relations can be used to estimate the coordination states of Te atoms in unknown Te crystals and glasses.

Structure and luminescent properties of complex compounds of tellurium(IV) with ammonium bases

Using tellurium(IV) complex compounds with outer-sphere ammonium cations as an example, we have studied the interrelation between their geometric structure and spectral-luminescent properties. In the series of compounds of tellurium(IV), which are characterized by the island octahedral coordination of Te(IV) ions, the luminescence intensity has been found to depend on the degree of distortion of the coordination polyhedron of the Te(IV) ion, the position of the A band in diffuse reflection spectra, and the energy of the luminescence transition 3 P 1 → 1 S 0 of the tellurium(IV) ion. We have revealed that the considered Te(IV) complexes possess reversible thermochromic properties.

Te(II)/Te(IV) Mediated C-N Bond Formation on 2,5-Diphenyltellurophene and a Reassignment of the Product from the Reaction of PhI(OAc)2 with 2 TMS-OTf.

We report a novel C-H to C-N bond metathesis at the 3-position of 1,2-diphenyltellurophene via oxidation of the Te(II) center to Te(IV) using the I(III) oxidant [PhI(4-DMAP)2](2+). Spontaneous reduction of a transient Te(IV) coordination compound to Te(II) generates an electrophilic equivalent of 4-DMAP that substitutes at a C-H bond at the 3-position of the tellurophene. Theoretical and synthetic reaction pathway studies confirm that a Te(IV) coordination complex with 4-DMAP is an intermediate. In the course of these pathway studies, it was also found that the identity of the I(III) oxidant generated from PhI(OAc)2 and 2 TMS-OTf is PhI(OAc)(OTf) and not PhI(OTf)2, as had been previously thought.

Tellurium speciation, connectivity, and chemical order in As(x)Te(100-x) glasses: results from two-dimensional 125Te NMR spectroscopy.

The short-range structure, connectivity, and chemical order in As(x)Te(100-x) (25 ≤ x ≤ 65) glasses are studied using high-resolution two-dimensional projection magic-angle-turning (pjMAT) (125)Te nuclear magnetic resonance (NMR) spectroscopy. The (125)Te pjMAT NMR results indicate that the coordination of Te atoms obeys the 8-N coordination rule over the entire composition range. However, in strong contrast with the analogous glass-forming As-S and As-Se chalcogenides, significant violation of chemical order is observed in As-Te glasses over the entire composition range in the form of homopolar As-As (Te-Te) bonds, even in severely As (Te)-deficient glasses. The speciation of the Te coordination environments can be explained with the dissociation reaction model As2Te3 → 2As + 3Te(II), characterized by a dissociation constant that is independent of glass composition. These structural characteristics can be attributed to the high metallicity of Te and the strong energetic similarity between the Te-Te, Te-As, and As-As bonds, and they are consistent with the monotonic and often nearly linear variation of physical properties observed in telluride glasses as a function of the Te content.

Network Rearrangement in AgI‐Doped GeTe4 Glasses

The structure of (GeTe4)1−x(AgI)x (x = 0.15 and 0.25) glasses has been investigated by X‐ray and neutron diffraction as well as extended X‐ray absorption spectroscopy (EXAFS) and Raman spectroscopy. Large‐scale structural models have been obtained by fitting simultaneously the experimental datasets in the framework of the reverse Monte Carlo simulation technique (RMC). Short‐range order parameters have been calculated and compared with that of GeTe4. Doping with AgI affects the structure of the host GeTe4 matrix in two ways. First, while Te is essentially twofold coordinated in GeTe4, its coordination number is as high as ~2.9 ± 0.3 for x = 0.25. The change is mainly due to the increased fraction of Te–Te bonds. Second, Ge atoms remain fourfold coordinated but the tetrahedral symmetry is distorted due to the elongation of some Ge–Te bonds. The incorporation of AgI in the GeTe4‐based host covalent matrix and the Te coordination increase explains the enhanced thermal stability of (GeTe4)1−x(AgI)x in the supercooled liquid‐state hindering the crystallization of Te found in case of GeTe4 glass.

Effect of concentration in Ge-Te liquids: A combined density functional and neutron scattering study

The structural properties of three compositions of Ge-Te liquids (${\mathrm{Ge}}_{10}{\mathrm{Te}}_{90}$, ${\mathrm{Ge}}_{15}{\mathrm{Te}}_{85}$, ${\mathrm{Ge}}_{20}{\mathrm{Te}}_{80}$) are studied from a combination of density functional based molecular dynamics simulations and neutron scattering experiments. We investigate structural properties including structure factors, pair distribution functions, angular distributions, coordination numbers, neighbor distributions and compare our results with experimental findings. Most noticeable is the good agreement found in the reproduction of the structure in real and reciprocal space, resulting from the incorporation of dispersion forces in the simulation. This leads to Ge and Te coordination numbers which are lower than in previous studies and which can now be followed with temperature, while also strongly depending on the chosen cutoff distance. Results show a gradual conversion of higher coordinated species (Te${}^{\text{IV}}$, Ge${}^{\text{V}}$) into lower coordinated ones at lower temperature, while leaving anticipated coordinations from the octet rule (Te${}^{\text{II}}$ and Ge${}^{\text{IV}}$) nearly unchanged. Structural correlations are characterized as a function of temperature and composition. The vibrational density of states is also measured from inelastic neutron scattering for different compositions and temperatures, and compared to the simulated counterpart which exhibits a reasonable agreement at low frequency.

Short‐Range Order in Ge–As–Te Glasses

The structure of Te‐rich (75–80 at.% Te) and Te‐poor (40 at.% Te) Ge–As–Te glasses has been investigated by diffraction and extended X‐ray absorption fine structure (EXAFS) measurements. Large‐scale structural models have been created by fitting simultaneously diffraction and EXAFS datasets by the reverse Monte Carlo simulation technique. It is found that As–As bonds improve the fit quality in the case of Te‐rich glasses while no Ge–Ge bonding is necessary in these compositions. In the Te‐poor glasses, Te–Te homopolar bonds are also observed while Ge binds preferentially to Te rather than to As. Ge–As and Ge–Te coordination numbers do not change significantly with increasing Ge content.

Revised values of the bond-valence parameters for TeIV—O, TeVI—O and TeIV—Cl

Bond-valence parameters r0 and b have been re-determined for Te(IV)-O: r0 = 1.9605 Å, b = 0.41; Te(VI)-O: r0 = 1.921 Å, b = 0.56; and Te(IV)-Cl: r0 = 2.3115 Å, b = 0.555. Bond distance data from 208 independent Te(IV)-O polyhedra, 118 Te(VI)-O polyhedra and 26 Te(IV)-Cl polyhedra were used, and all neighbours out to 3.5 Å were included. Root-mean square deviations of bond-valence sums on Te from ideal values were 0.1934, 0.1939 and 0.0865 v.u. The good fit for Te(IV)-O over a range of Te coordination numbers from 3 to 12 demonstrates that there is no essential difference in character between short `primary' Te-O bonds, oriented away from the Te lone pair, and longer `secondary' Te-O bonds on the same side of the Te atom as the lone pair. Comparison of bond-valence sums for Te-O polyhedra obtained using the new parameters with those calculated using earlier literature values shows that the new parameters give a narrower spread of calculated bond-valence sums, which means much closer to the formal valence for both oxidation states of tellurium.

XAS evidence for the stability of polytellurides in hydrothermal fluids up to 599 C, 800 bar

Although the crustal abundance of tellurium (Te) is about half of that of gold (Au), several classes of Au deposits are highly enriched in Te. Our understanding of the nature of this Au-Te association is hampered by the lack of experimental studies of Te geochemistry at elevated temperature. We characterized the structure of polytelluride solutions from room temperature to 599 °C at 800 bar using in situ X-ray absorption spectroscopy. Both ab-initio XANES and EXAFS fits show that polytellurides are stable up to the highest temperature, with planar structures (four- or threefold coordination of Te) giving way to linear chains (e.g., Te2-2ion) at temperatures above ~200 °C. This is the first experimental confirmation of the thermal stability of polytelluride species. The data show that polytellurides play an important role in Te transport in reduced S-rich or CO2-rich solutions and vapors.

Amorphous Ge15Te85: density functional, high-energy x-ray and neutron diffraction study

The structure and electronic properties of amorphous Ge15Te85 have been studied by combining density functional (DF) simulations with high-energy x-ray and neutron diffraction measurements. Three models with 560 atoms have been constructed using reverse Monte Carlo methods constrained to (1) agree with the experimental structure factors S(Q), and have (2) energies close to the DF minimum and (3) a semiconducting band structure. The best structure is based on the melt-quenched DF structure and has a small number of Ge–Ge bonds. It shows interlocking networks of Te and GeTe with a significant fraction (22–24%) of voids (cavities). Ge occurs with both tetrahedral and 3 + 3 defective octahedral configurations, and the coordination of Te is slightly higher than indicated by the ‘8 − N rule’ (N is the number of valence electrons). The GeTe network includes clusters of ABAB squares (A = Ge, B = Te), and the bonding is characterized by the chemical bond orders.

The Cu and Te coordination environments in Cu-doped Ge–Te glasses

The structure of Ge 20Te 80, Ge 15Cu 8Te 77 and Ge 15Cu 5Te 80 glasses was investigated by diffraction techniques and extended X-ray absorption fine structure measurements. Large structural models were generated by fitting experimental data by the reverse Monte Carlo simulation technique. In Ge 20Te 80 glass, both Ge and Te obey the 8 − N rule, and the structure is built up of GeTe 4 tetrahedra connected via Te–Te bonding or shared Te atoms connected to two Ge atoms. The coordination number of Te is significantly higher than 2 in Ge 15Cu 8Te 77. The average coordination number of Cu is 3.41 ± 1 in this alloy. In Ge 15Cu 5Te 80 glass, Cu binds mostly to Te, while Cu–Cu bonding is significant in Ge 15Cu 8Te 77.

The structure and optical dispersion of the refractive index of tellurite glass

The structure and optical properties of a 80TeO 2–(20− x)Li 2O– xTiO 2 glass system where x = 0, 5, 10, and 15 mol% has been investigated using FTIR spectroscopy and Brewster angle measurements. The sample preparation, linear refractive index and density measurements, and infrared spectroscopic analysis are described. The refractive index and density of the studied tellurite glass samples increase when the amount of Ti in the glass is increased. The dispersion of the phase refractive index was analyzed using Wemple’s model. The dispersion energy E d is significantly affected by the addition of Ti to TeO 2-based glass. The analysis of FTIR spectra indicate a Te coordination change that is in agreement with the increase of the Te coordination number determined from dispersion data using Wemple’s equation.

Structure and luminescence properties of tellurium(IV) complex compounds

Using the tellurium(IV) complex compounds as an example, we study the interrelation between the geometric structure and spectral luminescence properties. We find that, in the series of compounds of Te(IV), which are characterized by the island octahedral coordination of Te(IV) ions, the luminescence intensity depends on the degree of distortion of the Te(IV) coordination polyhedron, the Stokes shift, and the energy of the luminescence transition. We revealed that the considered series of Te(IV) compounds possess reversible thermochromic properties.

Microscopic origin of demixing in Ge 20Se xTe 80− x alloys

The structure of Ge 20Se x Te 80− x ( x = 5, 10, 15, 20) glasses has been investigated by X-ray and neutron diffraction as well as Ge and Se K-edge extended X-ray absorption fine structure (EXAFS) measurements. Experimental datasets have been fitted simultaneously by the reverse Monte Carlo simulation technique. It has been found that all components obey the 8-N rule. Se binds preferentially to Ge. At x = 20, experimental data can be fitted without Se–Te bonding, but Se–Se bonds appear, and the Te–Te coordination number starts to increase. These observations show that though Se and Te are completely miscible in the liquid and in the solid phases the presence of Ge induces nanoscale phase separation.