Mulliken occupation as the indicator of transition to superconducting state in SrFe2As2 and BaFe2As2

Basing on the ab initio calculations performed within full potential local orbital minimum basis method, the Mulliken occupation of the Sr 5s (n5s) and Ba 6p (n6p) states can serve as an indicator of transition to the superconducting state in doped SrFe2As2 and BaFe2As2 compounds where the iron was substituted with cobalt or in the pristine compounds under pressure. The estimated pressure, at which both compounds exhibit superconductivity based on Sr 5s and Ba 6p occupation is in good agreement with the recently published experimental data

Lanthanide Contraction in RENi 5 (RE = La, Ce, Nd, Sm, Eu, Gd, Tb, Yb) compounds studied with band structure calculations

Full potential linearized augmented plane wave band structure calculations were performed for hexagonal RENi5 (RE = rare earth) compounds in order to investigate reproducibility of lanthanide contraction by ab initio studies. The a and c parameters were optimised using a paraboloid t, starting from the same initial values for all compounds studied. The trend in lattice parameters across the RE series obtained from the calculations was found to be in general agreement with experimental data. A comparison of results obtained by generalized gradient approximation and generalized gradient approximation with additional Coulomb correlations calculations is presented for several double counting schemes

“DistorX” program for analysis of structural distortions affecting X-ray diffraction patterns

For the purposes of research on strongly correlated electronic systems (SCES), a computer program, DistorX (Distortion or X-ray diffraction patterns), was created. The program is an interactive Jupyter notebook for simulating the effects of structural distortions on X-ray diffraction patterns. The program is designed to be universal, in that it may be successfully applied to a variety of structures. In previous reports, a structural transition from a cubic phase of Yb3Rh4Sn13 – type to the superlattice variantwas been observed at 160 K for a series of skutterudite-related Ce3M4Sn13 compounds, where M = Co, Ru or Rh. In this work, we use a specialized build of DistorX to simulate the low-temperature X-ray diffraction patterns of a distorted unit cell. The method described here obtains simulated XRD patterns from the atomic positions and permits investigation of crystal structure without imposed symmetry operations. We further indicate the crystallographic plane in which the distortion occurs, and explain the possible origin of CDW in these materials

Thermoelectric properties of Ca2Sn/Ca3SnO

This type of materials was first synthesized in 1961 (Eckerlin), and its structure was determined by XRD measurements [1]. There are little experimental studies of thermodynamic and electrical properties of these compounds [2–4], as even in the first paper it was observed that these materials within a very short time turn into black powder after exposure to air. That powder contains mainly oxidation products. Recently, these materials were studied using ab-initio calculations and they were predicted to possess very promising thermopower [5–10]. Its real crystal structure is also a matter of debate [3, 8, 9]. The usability of thermoelectric material for thermoelectric applications depend on figure of merit, where high thermopower, small thermal conductivity and low resistivity is expected from a prospective material [11, 12]. Due to recent ab-initio studies we decided to revisit Ca2Sn, and measure its thermoelectric properties[…

Studies of electronic structure across a quantum phase transition in CeRhSb_{1-x}Sn_{x}

We study an electronic structure of CeRhSb1xSnx system, which displays quantum critical transition from a Kondo insulator to a non-Fermi liquid at x = 0:13. We provide ultraviolet photoelectron spectra of valence band obtained at 12.5 K. A coherent peak at the Fermi level is not present in the data, but a signal related to 4f1 7=2 nal state is detected. Spectral intensity at the Fermi edge has a general tendency to grow with Sn content. Theoretical calculations of band structure are realized with full-potential local-orbital minimum-basis code using scalar relativistic and full relativistic approach. The calculations reveal a depletion of density of states at the Fermi level for CeRhSb. This gap is shifted above the Fermi energy with increasing Sn content and thus a rise of density of states at the Fermi level is re ected in the calculations. It agrees with metallic properties of compounds with larger x. The calculations also yield another important e ect of Sn substitution. Band structure is displaced in a direction corresponding to hole doping, although with deviations from a rigid band shift scenario. Lifshitz transitions modify a topology of the Fermi surface a few times and a number of bands crossing the Fermi level increases

Thermoelectric properties of heavy fermion compound Ce3Co4Sn13

The heavy fermion compound Ce3Co4Sn13 was studied in terms of its thermoelectric properties. To enhance its gure of merit we milled the solid sample and then pressed to obtain a consistent granulated material. The main properties, such as the Seebeck coe cient, thermal conductivity and electronic resistivity were measured at low (< 300 K) temperatures for both, the solid and the granulated sample. Thermal conductivity was diminished and the Seebeck coe cient was slightly enhanced, while the resistivity of produced material was increased. We explain it by strong electron scattering on defects and grain boundaries present in the sample. The resulting gure of merit ZT was found to be enhanced almost across the whole measured T region

Electronic structure of TmPdIn

Electronic structure of a ternary TmPdIn compound, which crystallizes in the hexagonal ZrNiAl-type structure, was studied by X-ray photoemission spectroscopy and ultraviolet photoemission spectroscopy. Density of states in the valence band was calculated by means of the augmented plane wave/local orbital method based on density functional theory. The results showed that the valence band is formed mainly of Tm 4f and Pd 4d states. In the ultraviolet photoemission spectra one can distinguish Pd 4d maximum and Tm 4f multiplet peaks, which are displaced with respect to those of pure Tm

Specific heat and magnetic properties of single-crystalline (Zn0.925In0.054)[Cr1.84In0.152]Se-4 semiconductor

An antiferromagnetic order with a Néel temperature TN = 17:5 K, a strong ferromagnetic exchange evidenced by a positive Curie Weiss temperature CW = 77:3 K, the fuzzy peaks in the real component of susceptibility x′ (T) and the disappearance of the second critical eld were established. The curvature of speci c heat C(T) and C(T)=T in surrounding of TN indicated a broad peak, characteristic for the system with inhomogeneous magnetic state (spin-glass-like phase). The calculated magnetic entropy showed the value of S(T) 1 J/(mol K) which is extremely small; i.e., much lower than the magnetic contribution Rln(2S + 1) = 11:52 J/(mol K) calculated for the spin 3/2

Valence band of Ce2Co0.8Si3.2Ce_{2}Co_{0.8}Si_{3.2} and Ce2RhSi3Ce_{2}RhSi_{3} studied by resonant photoemission spectroscopy and FPLO calculations

This work presents studies of the valence band of two Kondo lattice systems: Ce2Co0.8Si3.2, which is paramagnetic with the Kondo temperature T-K approximate to 50 K and Ce2RhSi3, which is antiferromagnetic below T-N = 4.5 K and exhibits TK approximate to 9 K. The photoemission spectra, which are obtained with photon energy tuned to Ce - 4d 4f resonance, reveal a Kondo peak at the Fermi energy (E-F), its spin orbit splitting partner at 0.24 eV and a broad maximum related to Ce f(0) final state. The spectra indicate that Kondo peak has a higher intensity for Ce2Co0.8Si3.2. The off-resonance photoemission data reveal that a maximum in the 3d electron density of states is shifted towards EF for Ce2Co0.8Si3.2 as compared to Ce2RhSi3. Full-potential local-orbital calculations were realized with local spin density approach +U approach for 213 stoichiometry. They show that a higher density of states near EF is observed for Ce2CoSi3. The calculations also reveal the existing tendencies for antiferromagnetic and ferromagnetic ground states in a case of Ce2RhSi3 and Ce2CoSi3, respectively

Dipole Relaxation in Semiconducting Zn2−xMgxInV3O11 Materials (Where x = 0.0, 0.4, 1.0, 1.6, and 2.0)

This paper reports on the electrical and broadband dielectric spectroscopy studies of Zn2xMgxInV3O11 materials (where x = 0.0, 0.4, 1.0, 1.6, 2.0) synthesized using a solid-state reaction method. These studies showed n-type semiconducting properties with activation energies of 0.147–0.52 eV in the temperature range of 250–400 K, symmetric and linear I–V characteristics, both at 300 and 400 K, with a stronger carrier emission for the matrix and much less for the remaining samples, as well as the dipole relaxation, which was the slowest for the sample with x = 0.0 (matrix) and was faster for Mg-doped samples with x > 0.0. The faster the dipole relaxation, the greater the accumulation of electric charge. These e ects were analyzed within a framework of the DC conductivity and the Cole–Cole fit function, including the solid-state density and porosity of the sample. The resistivity vs. temperature dependence was well fitted using the parallel resistor model. Our ab initio calculations also show that the bandgap increased with the Mg content