Full-potential nonorthogonal local-orbital minimum-basis band-structure scheme

Koepernik, Klaus; Eschrig, H.

doi:10.1103/physrevb.59.1743

Cited by 2,050 publications

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“…21 For the total energy and band structure calculations based on the experimentally determined structures, the fullpotential local orbital code FPLO was applied. 22 The calculated band gaps are listed in Table 2. The orbital projected density of states (PDOS) for CsGaS 3 , Cs 2 Ga 2 S 5 , and CsGaS 2 -mC16 is shown in Figure 5.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…The first-principles calculations were carried out within the framework of density functional theory (DFT) with exchange-correlation functionals in the generalized gradient approximation (GGA) according to Perdew−Burke−Ernzerhof (PBE). 21 The full potential local orbital code FPLO14 22 was applied for total energy and band structure calculations based on the experimentally obtained structures. A k-grid mesh of 12 × 12 × 12 was used.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

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Interconversion of One-Dimensional Thiogallates Cs₂[Ga₂(S₂)_2–xS_2+x] (x = 0, 1, 2) by Using High-Temperature Decomposition and Polysulfide-Flux Reactions

Friedrich

Schlösser

Pfitzner

2017

Crystal Growth & Design

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The potential of cesium polysulfide-flux reactions for the synthesis of chalcogenogallates was investigated by using X-ray diffraction and Raman spectroscopy. An investigation of possible factors influencing the product formation revealed that only the polysulfide content x in the Cs 2 S x melts has an influence on the crystalline reaction product. From sulfur-rich melts (x > 7), CsGaS 3 is formed, whereas sulfur-poor melts (x < 7) lead to the formation of Cs 2 Ga 2 S 5 . In situ investigations using hightemperature Raman spectroscopy revealed that the crystallization of these solids takes place upon cooling of the melts. Upon heating, CsGaS 3 and Cs 2 Ga 2 S 5 release gaseous sulfur due to the degradation of S 2 2− units. This decomposition of CsGaS 3 to Cs 2 Ga 2 S 5 and finally to CsGaS 2 -mC16 was further studied in situ by using high-temperature X-ray powder diffraction. A combination of the polysulfide reaction route and the high-temperature decomposition leads to the possibility of the directed interconversion of these thiogallates. The presence of disulfide units in the anionic substructures of these thiogallates has a significant influence on the electronic band structures and their optical properties. This influence was studied by using UV/vis-diffuse reflectance spectroscopy and DFT simulations, revealing a trend of smaller band gaps with increasing S 2 2− content. ■ INTRODUCTIONGroup 13 chalcogenometallates containing alkali metal cations M x T y Q z (M = alkali metal, T = triel, Q = chalcogen) are interesting materials due to their semiconducting properties. These materials are used, e.g., in gas sensors or detectors for high-energy radiation. 1 The crystal structures of most compounds in the ternary systems M−T−Q consist of oligomeric or polymeric one-, two-, or three-dimensional (1D, 2D, 3D) anions formed by condensed TQ 4 tetrahedra. 2 Among the large number of chalcogenotrielates, however, only a few compounds featuring polychalcogenide units are known. Incorporation of polychalcogenide units into the anionic structures leads to more exotic structural motives. The crystal structures of mixed-valent chalcogenometallates like CsGaQ 3 , 3,4 Cs 2 Ga 2 Q 5 , 5,6 CsAlTe 3 7 and several chalcogenoborates 8−11 show 1D anionic chains containing Q 2 2− or Q 3 2− units (Q = S, Se). The mixed-valent nature of the chalcogen in these compounds should significantly influence the properties of these semiconductors. Therefore, it is necessary to understand the reactive behavior of these compounds and the conditions necessary for their formation in order to design compounds with desired properties. Molten polysulfide fluxes are an established method for the synthesis of substances featuring polysulfide anions. 12−14 Due to an enhanced diffusion rate at comparably low temperatures in these fluxes, the formation of thermodynamically metastable compounds is favored as compared to high-temperature reactions. Furthermore, the properties of these fluxes (basicity, viscosity, etc.) can be fine-tuned by adjusti...

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Experimental Sectionmentioning

confidence: 99%

Interconversion of One-Dimensional Thiogallates Cs₂[Ga₂(S₂)_2–xS_2+x] (x = 0, 1, 2) by Using High-Temperature Decomposition and Polysulfide-Flux Reactions

Friedrich

Schlösser

Pfitzner

2017

Crystal Growth & Design

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“…Two all-electron full-potential codes, FPLO-9 25 and WIEN2k 26 based on the augmented plane wave+local orbitals (APW+lo) method, 27 have been used in these calculations, with consistent results. The Brillouin zone was sampled with regular 12 × 12 × 12 k-mesh during self-consistency.…”

Section: Methodsmentioning

confidence: 99%

Linear bands, zero-momentum Weyl semimetal, and topological transition in skutterudite-structure pnictides

2012

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It was reported earlier [Phys. Rev. Lett. 106, 056401 (2011)] that the skutterudite structure compound CoSb3 displays a unique band structure with a topological transition versus a symmetrypreserving sublattice (Sb) displacement very near the structural ground state. The transition is through a massless Dirac-Weyl semimetal, point Fermi surface phase which is unique in that (1) it appears in a three dimensional crystal, (2) the band critical point occurs at k=0, and (3) linear bands are degenerate with conventional (massive) bands at the critical point (before inclusion of spin-orbit coupling). Further interest arises because the critical point separates a conventional (trivial) phase from a topological phase. In the native cubic structure this is a zero-gap topological semimetal; we show how spin-orbit coupling and uniaxial strain converts the system to a topological insulator (TI).We also analyze the origin of the linear band in this class of materials, which is the characteristic that makes them potentially useful in thermoelectric applications or possibly as transparent conductors. We characterize the formal charge as Co + d 8 , consistent with the gap, with its 3 site symmetry, and with its lack of moment. The Sb states are characterized as px (separately, py) σ-bonded Sb4 ring states occupied and the corresponding antibonding states empty. The remaining (locally) pz orbitals form molecular orbitals with definite parity centered on the empty 2a site in the skutterudite structure. Eight such orbitals must be occupied; the one giving the linear band is an odd orbital singlet A2u at the zone center. We observe that the provocative linearity of the band within the gap is a consequence of the aforementioned near-degeneracy, which is also responsible for the small band gap.

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“…Density of states (DOS) for the CeNi 9 In 2 compound was calculated using full potential local orbital (FPLO) code in the scalar relativistic version [10]. For the calculations the PerdewWang exchange -correlation potential was applied [11,12].…”

Section: Methodsmentioning

confidence: 99%

Electronic structure and transport properties of CeNi9In2

Kurleto

Starowicz

Goraus

et al. 2015

Solid State Communications

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We investigated CeNi 9 In 2 compound, which has been considered as a mixed valence (MV) system. Electrical resistivity vs. temperature variation was analysed in terms of the model proposed by Freimuth for systems with unstable 4f shell. At low temperature the resistivity dependence is consistent with a Fermi liquid state with a contribution characteristic of electron-phonon interaction. Ultraviolet photoemission spectroscopy (UPS) studies of the valence band did not reveal a Kondo peak down to 14 K. A difference of the spectra obtained with photon energies of low and high photoionization cross sections for Ce 4f electrons indicated that 4f states are located mainly close to the Fermi energy. The peaks related to f 5/2 1 and f 7/2 1 final states cannot be resolved but form a plateau between -0.3 eV and the Fermi energy. X-ray photoemission spectroscopy (XPS) studies were realized for the cerium 3d level. The analysis of XPS spectra within the Gunnarsson-Shönhammer theory yielded a hybridization parameter of 104 meV and non-integer f level occupation, being close to 3. Calculations of partial densities of states were realized by a full potential local orbital (FPLO) method. They confirm that the valence band is dominated by Ni 3d states and are in general agreement with the experiment except for the behavior of f-electrons.

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Full-potential nonorthogonal local-orbital minimum-basis band-structure scheme

Cited by 2,050 publications

References 30 publications

Interconversion of One-Dimensional Thiogallates Cs₂[Ga₂(S₂)_2–xS_2+x] (x = 0, 1, 2) by Using High-Temperature Decomposition and Polysulfide-Flux Reactions

Interconversion of One-Dimensional Thiogallates Cs₂[Ga₂(S₂)_2–xS_2+x] (x = 0, 1, 2) by Using High-Temperature Decomposition and Polysulfide-Flux Reactions

Linear bands, zero-momentum Weyl semimetal, and topological transition in skutterudite-structure pnictides

Electronic structure and transport properties of CeNi9In2

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Full-potential nonorthogonal local-orbital minimum-basis band-structure scheme

Cited by 2,050 publications

References 30 publications

Interconversion of One-Dimensional Thiogallates Cs2[Ga2(S2)2–xS2+x] (x = 0, 1, 2) by Using High-Temperature Decomposition and Polysulfide-Flux Reactions

Interconversion of One-Dimensional Thiogallates Cs2[Ga2(S2)2–xS2+x] (x = 0, 1, 2) by Using High-Temperature Decomposition and Polysulfide-Flux Reactions

Linear bands, zero-momentum Weyl semimetal, and topological transition in skutterudite-structure pnictides

Electronic structure and transport properties of CeNi9In2

Contact Info

Product

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Interconversion of One-Dimensional Thiogallates Cs₂[Ga₂(S₂)_2–xS_2+x] (x = 0, 1, 2) by Using High-Temperature Decomposition and Polysulfide-Flux Reactions

Interconversion of One-Dimensional Thiogallates Cs₂[Ga₂(S₂)_2–xS_2+x] (x = 0, 1, 2) by Using High-Temperature Decomposition and Polysulfide-Flux Reactions