Density variations in liquid tellurium: Roles of rings, chains, and cavities

Abstract

Liquid tellurium has been studied by density-functional/molecular-dynamics simulations at 560, 625, 722, and 970 K and by high-energy x-ray diffraction ͑HEXRD͒ at 763 K and 973 K. The HEXRD measurements agree very well with earlier neutron-scattering data of Menelle et al. The density maximum near the melting point ͑722 K͒ reflects the competition between twofold and threefold local coordination, which results in chain formation and changed ring statistics at lower T, and the variation with T of the volume of cavities ͑26-35 % of the total͒. A higher-order gradient expansion of the exchange-correlation functional is needed to describe structural details. Changes in the electronic properties ͑band gap and dc conductivity͒ upon cooling are consistent with a transition from a high-temperature metal to a semiconductor.

Communication: Van der Waals corrections for an improved structural description of telluride based materials

“…One thus realizes that an attractive van der Waals correction leads to an increase of the intensity of the secondary peak in both g TeTe and g GeTe but slightly reduces the interchain distance. As this peak is indeed usually assigned to the Te interchain distance, 9 it indicates that the VdW simulated liquid contains a better separation between the Te-chains. Having the pair distribution functions g ij at our disposal and given the respective weight of the partials g GeGe , g GeTe , and g TeTe (0.04, 0.32, 0.64, respectively), it becomes clear that the reproduction of the secondary peak of g(r) in the VdW simulation (and absent in the no-VdW simulation, see Fig.…”

“…7,8 In order to characterize these basic phenomena and to understand the observed anomalies, a certain number of computational studies using First Principles Molecular Dynamics (FPMD) and density functional theory (DFT) have been reported on, e.g., elemental Te 9 and on tellurium based alloys. [10][11][12][13][14] Unfortunately, FPMD usually overestimates the bond distances and atomic neighbors in telluride systems so that computed standard structural signatures (pair distribution function g(r), structure factor S(k)) fail to agree [9][10][11][12][13][14] with corresponding experimental measurements from X-ray or neutron diffraction. [15][16][17] Among various flaws, one should note that in Ge 15 Te 85 the first peak of the pair distribution function g(r) corresponding to the Ge-Te bond distance is usually found at 2.78−2.85 Å, 10,14 to be compared with the measured value of 2.75 Å (at 673 K, Ref.…”

Structure and dynamics in liquid bismuth and Bin clusters: A density functional study

“…The ratio r 2 /r 1 decreases with increasing atomic number, 1 an effect also found in group 16 elements (S, Se, Te, Po) for the ratio of "interchain" to "intrachain" distances. 3 The variety of structural patterns and other properties has made group 15 elements attractive objects of study for decades. [5][6][7] Eighty years ago, Jones 8,9 explained the high diamagnetism, low (semimetallic) conductivity, and structure of bismuth as a distortion of a simple cubic structure brought about by the existence of a large (Jones) zone containing five valence electrons per atom.…”

“…It has been used frequently to test relativistic effects in molecular and solid state calculations, including wave function based calculations of the dimer 30,31 and trimer. 32 The results of coupled-cluster and density functional calculations have been compared for Bi 3 , 33 but almost all recent theoretical work on Bi n clusters and their ions have used DF methods. The most extensive include Sb − n and Bi − n to n = 13, 34 Bi n and Bi + n to n = 24, 35 Bi n and Bi − n to n = 13, 36 Bi n to n = 14, 37 and Bi + n to n = 14.…”

Visualizing the Mixed Bonding Properties of Liquid Boron with High-Resolution X-Ray Compton Scattering

“…The experimental and theoretical approaches discussed in the present study provide new tools of wide applicability for investigating the nature of bonding in high temperature liquids. For instance, WFSDs could also provide useful information for liquid tellurium despite the fact that the treatment of higher atomic systems is more difficult [37].…”