Elastic properties and inter-atomic bonding in new superconductor from first principles calculations

Shein, I. R.; Ivanovskiĭ, A. L.

doi:10.1016/j.ssc.2011.02.024

Cited by 12 publications

(10 citation statements)

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“…The data [93] reveal that KFe 2 Se 2 is a relatively soft material. Note also that the elastic moduli of KFe 2 Se 2 are comparable on the whole with the same for other layered Fe-As SC's.…”

Section: Elastic Propertiesmentioning

confidence: 89%

“…The results show that KFe 2 Se 2 is a partly ionic compound, and charges are transferred from K and Fe to Se; besides, charge transfer occurs also from K 0.78+ sheets to [Fe 2 Se 2 ] 0.78blocks. In summary, the data [93] reveal that the inter-atomic bonding in this system is highly anisotropic and includes ionic, covalent, and metallic contributions, where mixed covalent-ionic Additional research is required for a more precise definition of the charge transfer in cation-deficient species such as charge-balanced K 0.8 Fe 1.6 Se 2 .…”

Section: Chemical Bondingmentioning

confidence: 98%

“…The peculiarities of inter-atomic bonding in 122 Fe-Se phases were discussed in Ref. [93] using the stoichiometric KFe 2 Se 2 as an example. From the DOSs picture ( Fig.…”

Section: Chemical Bondingmentioning

confidence: 99%

“…Within the simplified ionic model, the charge transfer (1e) from K 1+ sheets to [Fe 2 Se 2 ] 1blocks should be assumed if we use the usual oxidation numbers of atoms: K 1+ , Fe 2+ , and Se 2-. Within Bader [95] analysis, the effective charges were calculated [93]: ΔQ(K) = +0.78e, ΔQ(Fe) = +0.50e, and ΔQ(Se) = -0.89e. The results show that KFe 2 Se 2 is a partly ionic compound, and charges are transferred from K and Fe to Se; besides, charge transfer occurs also from K 0.78+ sheets to [Fe 2 Se 2 ] 0.78blocks.…”

Section: Chemical Bondingmentioning

confidence: 99%

“…Using the ab initio method, the authors [93] predicted the elastic properties for KFe 2 Se 2 as a parent phase for 122FeSe SCs. The values of six independent elastic constants (C ij ) for the tetragonal KFe 2 Se 2 (C 11 = 146 GPa, C 12 = 57 GPa, C 13 = 41 GPa, C 33 = 64 GPa, C 44 = 32 GPa, and C 66 = 68 GPa) are positive and satisfy the well-known Born's criteria [111] for mechanically stable tetragonal crystals: C 11 > 0, C 33 > 0, C 44 > 0, C 66 > 0, (C 11 -C 12 ) > 0, (C 11 + C 33 -2C 13 ) > 0, and {2(C 11 + C 12 ) + C 33 + 4C 13 } > 0.…”

Section: Elastic Propertiesmentioning

confidence: 99%

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New ternary ThCr2Si2-type iron–selenide superconducting materials: Synthesis, properties and simulations

Ivanovskiĭ

2011

Physica C: Superconductivity

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We report the superconductivity at above 30 K in a new FeSe-layer compound K 0.8 Fe 2 Se 2 (nominal composition) achieved by metal K intercalating in between FeSe layers. It is isostructural to BaFe 2 As 2 and possesses the highest T c for FeSe-layer materials so far under ambient pressure. Hall effect indicates the carriers are dominated by electron in this superconductor. We confirm that the observed superconductivity at above 30 K is due to this new FeSe-based 122 phase. Our results demonstrate that FeSe-layer materials are really remarkable superconductors via structure and carrier modulation. 74.70.Xa, 74.70.Dd, 74.20.Mn The discovery of superconductivity in the quaternary ZrCuSiAs-type (referred to as 1111-type) Fe-based oxypnictide LaFeAsO (F-doped) with critical temperature (T c ) 26 K has inspired worldwide interests on high temperature superconductors once more. we tried to grow single crystal by flux method. The precursors of the same stoichiometry were put into alumina crucibles and sealed in silica ampoules under an atmosphere of 0.2 bar argon. The samples were heated to 1300 K, cooled down to 1000 K at the rate of 4 K/hr and finally furnace-cooled to room temperature.Well-formed plates with shiny surfaces having dimensions up to 3 mm × 2 mm × 0.5 mm were obtained. The as-prepared samples were characterized by powder X-ray diffraction (PXRD) using a panalytical X'pert diffractometer with Cu K a radiation.Rietveld refinements of the data were performed with the FULLPROF package. 17 The electrical resistance and Hall coefficient were measured through the standard four-wire method and five-wire technique on the physical property measurement system (PPMS, Quantum Design), respectively. The dc magnetic properties were characterized using a vibrating sample magnetometer (VSM, Quantum Design). It should be noted that the electrical and magnetic properties were measured based on crystals. Figure 1 shows the diffraction pattern of polycrystalline sample collected at room 3 temperature. All the reflections could be indexed with lattice parameters a = b = 3.9136 (1) Å, c = 14.0367 (7) Å and V = 214.991 (13) The interlayer distance of two neighboring Fe-Fe square plane, 7.0184(5) Å, is the largest discovered so far, a consequence of K intercalated into FeSe layers.The increase in a-axis is significantly smaller than that of c-axis, which leads to the reduced dimensionality in KFe 2 Se 2 . As one of the most important structuralfeatures, the refinement indicates that the Fe-Se-Fe angle is 110.926(4)º, which is closer to the ideal angle of high symmetric tetrahedra compared to that of FeSe.The X-ray diffraction pattern of crystal (as shown in Fig. 2) is dominated by the 00l (l is nearly temperature independent. R H drops dramatically below 105 K, which is the exactly same temperature as the peak position observed in the resistive measurement.As FeAs-based superconductors, the strong temperature dependence below 105 K is 5 qualitatively anticipated by the gradual forming of gap in the Fermi surface.6...

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“…The data [93] reveal that KFe 2 Se 2 is a relatively soft material. Note also that the elastic moduli of KFe 2 Se 2 are comparable on the whole with the same for other layered Fe-As SC's.…”

Section: Elastic Propertiesmentioning

confidence: 89%

Section: Chemical Bondingmentioning

confidence: 98%

“…The peculiarities of inter-atomic bonding in 122 Fe-Se phases were discussed in Ref. [93] using the stoichiometric KFe 2 Se 2 as an example. From the DOSs picture ( Fig.…”

Section: Chemical Bondingmentioning

confidence: 99%

Section: Chemical Bondingmentioning

confidence: 99%

Section: Elastic Propertiesmentioning

confidence: 99%

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