We report on single crystal growth, single crystal x-ray diffraction, physical properties and density functional theory (DFT) electronic structure as well as Fermi surface calculations for two ternary carbides, LuCoC2 and LuNiC2. Electrical resistivity measurements reveal for LuNiC2 a charge density wave (CDW) transition at TCDW 450 K and, for T > TCDW, a significant anisotropy of the electrical resistivity, which is lowest along the orthorhombic a-axis. The analysis of x-ray superstructure reflections suggest a commensurate CDW state with a Peierls-type distortion of the Ni atom periodicity along the orthorhombic a-axis. DFT calculations based on the CDW modulated monoclinic structure model of LuNiC2 as compared to results of the orthorhombic parent-type reveal the formation of a partial CDW gap at the Fermi level which reduces the electronic density of states from N (EF) = 1.03 states/eV f.u. without CDW to N (EF) = 0.46 states/eV f.u. in the CDW state. The corresponding bare DFT Sommerfeld value of the latter, γ CDW DFT = 0.90 mJ/mol K 2 , reaches reasonable agreement with the experimental value γ = 0.83(5) mJ/mol K 2 of LuNiC2. LuCoC2 displays a simple metallic behavior with neither CDW ordering nor superconductivity above 0.4 K. Its experimental Sommerfeld coefficient, γ = 5.9(1) mJ/mol K 2 , is in realistic correspondence with the calculated, bare Sommerfeld coefficient, γDFT = 3.82 mJ/mol K 2 , of orthorhombic LuCoC2.
Sc5Ir6Sn18 crystallizes with a split variant of the Tb5Rh6Sn18 structure type (space group I41/acd, , ). DFT calculations confirmed the instability of the structural arrangement with the fully occupied and unsplit crystallographic sites. High quality single crystals were grown from a Sn melt. Sc5Ir6Sn18 is a diamagnetic metal showing a superconducting transition at a critical temperature K. The relatively low critical magnetic field 3.2 T as well as the obtained values of the specific heat ratio and energy-gap ratio suggest this system to be a weakly coupled BCS-like superconductor.
Abstract:The studies of the laser operated third order nonlinear optical features of novel TlGaSn 2 Se 6 crystal were done. The main efforts were devoted to a search of a possibility to apply these crystals as laser operated optoelectronic material. For this reason, the third harmonic generation of the Nd:YAG pulse laser 1064 nm as the fundamental beam with varied energy density of up to 200 J/m 2 was studied. As a source of laser operated light, we have used the cw laser (532 nm), exciting the material above the energy gap. Additionally, the influence of middle-energy Ar + ions on the XPS spectra of the TlInSn 2 Se 6 surface has been explored. We have shown that the main contribution of the Se4p states is manifested in the upper part of the valence band of TlInSn 2 Se 6 We have established that for the TlGaSn 2 Se 6 crystal there exists a possibility of variation of the third harmonic generation efficiency using illumination by external continuous wave laser beam. The discovered effect makes it possible to utilize TlGaSn 2 Se 6 crystal in advanced optoelectronic laser operated devices.
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