G. WENSKI's research while affiliated with University of Cologne and other places

... The ordered honeycomb network structure therefore appears to be favourable for the occurrence of superconductivity. In this paper, we report the discovery of superconductivity in CaPtAs with T c = 1.47 K, which adopts a noncentrosymmetric tetragonal structure consisting of twisted three-dimensional (3D) honeycombs of Pt-As along the c-axis [38]. ...

... Unfortunately, we were not able to do the structure determination for these compounds on single crystals at the time. Some preliminary results about the structure of Dy 12 Ni 30 As 21 and Tb 12 Ni 30 As 21 have been reported in literature [15], and finally the crystal structure of Dy 12 Ni 30 As 31 has been proposed in literature [16] as a (La, Ce) 12 Rh 30 P 21 -type related structure. ...

... Variations of / 0 and / 0 as functions of pressure are illustrated in figure 3, where ( ) is the lattice parameter (unit cell volume) at the considered pressure and 0 ( 0 ) is the corresponding value at zero pressure. The obtained results for / 0 and / 0 in the considered range of pressure are well fitted to a third-order polynomials: Ref [16], Ref [28], f [29], Ref [14], Ref [15], Ref [30], Ref [31], ℎ Ref [32]. ...

... Along these lines, it is interesting to note that in LaPtSb, the buckling is largely manifested in out-of-plane shifts of the Pt atoms, minimizing La-Sb collisions, while in LaAuGe, the smaller Ge atoms show greater displacement. These results also correlate with observations described in the literature for other AlB 2 -type variants, [38][39][40] where the degree of buckling in the crystal structures is often attributed to the size of the stuffing cation A. As the radius of the stuffing cation increases, c increases and interactions between the layers are reduced. With increasing atomic radii, the structures transition from a stuffed wurtzite network (LiGaGe-type) to stuffed graphite sheets (ZrBeSi-type). ...

... For the diverse physical properties shown in ternary rare Earth pnictides, these materials are appropriate candidates to study these novel quantum phenomena. Strangely, a few decades ago, YbPtAs [22,23] was reported to crystallize in an AlB 2 derived hexagonal structure, the same as SrPtAs, but there has been little study on the physical properties. In this case, the substitution of Sr with Yb would introduce a localized moment from 4 electrons, and the hybridization between the localized 4 -electrons and conduction electrons can produce exotic properties, like the heavy fermion superconductivity. ...

... CaPtAs is superconducting below T c = 1.47 K 146 , and has a noncentrosymmetric tetragonal structure consisting of a three-dimensional hexagonal network of Pt-As atoms, with the same chiral space group (I4 1 md) as a number of equiatomic ternary SC's RT X (R=La or Th, T =transition metal, X=Si, Ge, As or P) [147][148][149][150][151][152][153][154] . The structure of CaPtAs however is different from the LaPtSitype structure of the latter compounds, having a greatly elongated c-axis which is about three times longer 155 . ...

... 22,23) The k-point mesh is employed up to 24 ×24 ×16 (48 × 48 × 32) in the Brillouin zone (BZ) in scf (nscf) calculations, and the energy cutoff of wavefunctions is set to 100 Ryd. The lattice constants are given by a = 4.535 Å and c = 4.884 Å for BaPtSb, 24) and a = 4.308 Å and c = 4.761 Å for BaPtAs. 19) The obtained electronic structures are shown in Fig. 1. ...