Structural and bonding properties of solid tellurium from first-principles calculations

Abstract

%'e have studied the structural and bonding properties of the equilibrium and high-pressure phases of tellurium by means of Srst-principles total-energy calculations, performed within the localdensity approximation.The calculated characteristics of the various polymorphs under pressure show good general agreement with existing experiments. However, some systematic discrepancies occur between computed and measured structural parameters for the open linear-chain (trigonal) and layer-type (orthorhombic) phases. The interchain and interlayer distances are underestimated within the local-density approach, and the relative stability of the trigonal and of the orthorhombic phase with respect to compact metallic structures is lower in the calculations than indicated by the experimental phase diagram. The complex structural changes of Te under pressure are discussed in terms of the trends under pressure of the di6erent types of bonds involved in the various crystal structures.

Calculations of theA1Phonon Frequency in Photoexcited Tellurium

“…In general, the use of LDA band energies for excited states is complicated by the fact that the true (quasi-particle) excitation energies are not equal to the DFT eigenvalues. However, in this system the LDA gap (0.26 eV) is not too much different from the experimental band gap (0.33 eV [14]) and the band dispersions within the LDA conduction and valence are very similar to the experimentally determined dispersions [15]. Thus, the approximation of using the LDA excited bands to calculate the total energy of the photoexcited system is reasonably accurate in the present context.…”

Formation of Tellurium Nanocrystals during Anaerobic Growth of Bacteria That Use Te Oxyanions as Respiratory Electron Acceptors

“…In order to gain insight into the atomic structural arrangements within these Te nanocrystals, the extracellular tellurium "rosettes" from B. selenitireducens and the granular "nanospheres" from S. barnesii were cleansed of cellular material and compared with the commercially obtained Te(0) using Raman spectroscopy. Elemental Te is known to adopt a trigonal geometry with three tellurium atoms per unit cell under ambient conditions (ϳ20°C) (5,18). Each of these unit cells can then be characterized by an infinite helical chain oriented parallel to the x axis (Fig.…”

Microscopic structure and dynamics of molten Se50Te50 alloys

“…There is some shift in the phase of long wave vector oscillations due to errors in the ab initio estimation of the equilibrium nearest neighbor distance, i.e., in the location of the first g͑r͒ maximum, a well known limitation of the DFT calculation when dealing with Te atoms. 27,28 Despite this, we see that the temperature dependence of the height and location of the first and second maxima of S͑Q͒ is the same both in MD and in the experimental data. From Fig.…”

“…As to the bond angle XSeŶ whose distribution peaks around 100°, is somewhat lower than the experimental and ab initio values 30 found in molten Se ͑Ϸ110°͒. It seems that the accurate ab initio description of Se atoms somewhat compensates the deficiencies in the treatment of Te atoms ͑note that the stability of the cubic structure is overestimated 28 in the DFT for Te and this tends to favor bond angles close to 90°͒ as found in Ref. 29.…”

“…This can be explained by the well documented failure of DFT treatments to properly account for bonding in solid and liquid tellurium. 27,28 Additionally, these inaccuracies in the first TeTe coordination shell are likely to be responsible for the systematic underestimation of the second maximum of the total structure factor seen in Fig. 1.…”