[en] We have carried out an LAPW (using the muffin-tin approximation) and a full potential LAPW band-structure calculations for cubic LaFe₄P₁₂ and compared the results with recent dHvA measurements. The FLAPW result explains the experimental results better. (orig.)

[en] The electrical resistivity rho of the rare earth iron phosphides REFe₄P₁₂ (RE = La, Ce and Pr) has been determined as a function of temperature T. Although isostructural, the behavior of rho (T) is remarkably distinct for these three compounds. While LaFe₄P₁₂ is superconducting, CeFe₄P₁₂ exhibits a semiconductor-like behavior, and PrFe₄P₁₂ exhibits a feature at low temperatures that could be related to a combined structural and magnetic transition

[en] The phosphide oxide La_2AuP_2O was synthesized from lanthanum filings, dried La_2O_3, gold pieces, and ground red phosphorus in the ideal 1.33:0.33:1:2 ratio in an evacuated silica tube at 1473 K. Small single crystals were obtained by recrystallization in a NaCl/KCl flux. The structure was determined on the basis of single-crystal X-ray diffractometer data: new type, C2/m, a = 1537.3(3), b = 427.39(8), c = 1009.2(2) pm, β = 131.02(1) , wR_2 = 0.046, 1102 F"2 values, 38 variables. La_2AuP_2O contains two striking structural motifs: The oxygen atoms are located in La_4 tetrahedra. The latter are cis-edge-shared forming polymeric cationic [La_2O]"4"+ chains. These cationic units are separated and charge-balanced by [AuP_2]"4"- polyanions which have monovalent gold in distorted trigonal planar phosphorus coordination. Two crystallographically independent phosphorus sites occur in the polyanion, i.e. isolated P"3"- besides dumb-bells P_2"4"- (P2-P2 223 pm). La_2AuP_2O, which crystallizes in the form of ruby red transparent crystals, is an electron precise phosphide oxide (4La"3"+)(2Au"+)(2P"3"-)(P_2"4"-)(2O"2"-). (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

[en] The method of monocrystal investigation has been used to establish that the LaCo₅P₃ compound has a rhombic structure of a new type: a=0.3651+-0.0001; b=1.1573+-0.0002; c=1.1459+-0.0002 nm space group Cmcm. The refinement of atomic coordinates is carried out in 306 non-zero hkl reflexes up to R=0.054 in the anisotropic approximation. In the LaCo₅P₃ structure, phosphorus atoms are situated in the centres of a trigonal prisms formed by metal atoms. Trigonal prisms connected by ribs (in pairs or in threes) form corrugated walls 1/2 a shifted relatively to each other. The position of trigonal prisms in the LaCo₅P₃ structure is similar to that in the structure of the UNi₅Si₃ type. The coordinate numbers of La, Co and P atoms are 23, 12 and 9, respectively. La-Co interatomic distances are 0.322-0.351; La-P: 0.307-0.320; Co-Co: 0.241-0.268; Co-P: 0.216-0.238 nm

[en] The bandstructures and Fermi surfaces are calculated for LaFe₄P₁₂, LaFe₄As₁₂ and LaFe₄Sb₁₂, by using an FLAPW method. The density of states at the Fermi level increases from P to Sb, due to the rising of the relative position of the Fe-d(t_2g) bands, because of the increase of the interatomic distances

[en] La${}_2$SiP${}_4$ (mP-28, Z=4, Wyckoff sequence e${}^7$, space group P2${}_1$/c (No. 14), a=10.8230(6) Å, b=7.5208(4) Å, c=7.9189(4) Å, and β=105.389(2)°) which crystallizes in the La${}_2$CuS${}_4$ structure type is reported. Instead of isolated CuS${}_3$ triangles bridged by disulfide anions, in the crystal structure of La${}_2$SiP${}_4$, one-dimensional zig-zag chains composed of SiP${}_4$ tetrahedra connected by P-P bonds are present. Lanthanum cations fill the voids between the chains and are coordinated by either 9P or 8P+Si atoms. La2SiP4 is a narrow bandgap semiconductor with calculated and measured optical bandgaps of 0.35 eV and 0.85(1) eV, respectively. (© 2020 Wiley‐VCH GmbH)

[en] The completely unexplored LaP molecule is investigated by ab initio methods. Potential energy curves for the low-lying states of LaP are constructed by means of the diffusion Monte Carlo method combined with three different trial functions. Spectroscopic constants are also numerically derived and the ground state is assigned, looking forward to experimental comparisons. Moreover, variations of the permanent dipole moments as a function of the internuclear separation for the two lowest states of the diatomic LaP are studied and analyzed. (paper)

[en] The ternary compound LaFe₄P₁₂ having a ''filled skutterudite'' structure is a superconductor with T/sub c/ = 4.08 K. We have used the Moessbauer effect of ⁵⁷Fe to show that the magnetic moment of Fe in LaFe₄P₁₂ is less than 0.01μ/sub B/. The value of the measured isomer shift indicates a spin-paired 3d configuration of Fe. The temperature dependence of the shift and the resonance fraction are used to establish a weak coupling of 3d electrons with the phonons, the coupling parameter being about 0.4 to 0.5

[en] The superconducting transition temperature, Tsub(c), of the LaT₄P₁₂ compounds with T = Fe, Ru, or Os has been measured under hydrostatic pressure P up to 1.8 GPa. The T=Fe compound exhibits a substantial increase of Tsub(c) from Tsub(c) (P-O) = 4.1 K at a rate (dTsub(c)/dP)sub(P=O) = +7.2 x 10^-1 K/GPa. In contrast, the Ru and Os compounds exhibit only weak decreases of Tsub(c) from Tsub(c) (P=O) = 7.2 K and 1.8 K with (dTsub(c)/dP)sub(P=O) = -1.6 x 10^-1 K/GPa and -9.5 x 10^-2 K/GPa, respectively. An analysis of this strikingly divergent behavior of Tsub(c)(P) in terms of the structural characteristics of the RT₄X₁₂ class of compounds where R = rare earth element, T = Fe, Ru, or Os, and X = P, As, or Sb suggests that Tsub(c)(P) for these materials consists of two competing contributions: a depression of Tsub(c) due to the compression of the lattice (i.e., decrease in volume), and an enhancement of Tsub(c) due to the effect of pressure on La itself. (author)

[en] Full potential linearized augmented plane wave plus local orbital method (FPLAPW+lo) calculations were performed for LaFe₄P₁₂ in the filled skutterudite in order to investigate the optical properties and to show the origin of the different optical transitions. It is found that the band gap is indirect for LaFe₄P₁₂. Then the contribution of the different transitions peaks is analyzed from the imaginary part of the dielectric function. In contrast to recent experimental expectations, our calculations are in good agreement with experimental reflection spectra and ε ₁(ω) spectrum