La₅Zn₂Sn

Abstract

Key indicators: single-crystal X-ray study; T = 293 K; mean (La-Zn) = 0.001 Å; R factor = 0.027; wR factor = 0.056; data-to-parameter ratio = 29.9.A single crystal of pentalanthanum dizinc stannide, La 5 Zn 2 Sn, was obtained from the elements in a resistance furnace. It belongs to the Mo 5 SiB 2 structure type, which is a ternary ordered variant of the Cr 5 B 3 structure type. The space is filled by bicapped tetragonal antiprisms from lanthanum atoms around tin atoms sharing their vertices. Zinc atoms fill voids between these bicapped tetragonal antiprisms. All four atoms in the asymmetric unit reside on special positions with the following site symmetries: La1 (..m); La2 (4/m..); Zn (m.2m); Sn (422). Related literature ExperimentalCrystal data The way of bond formation in this compound was assumed using only X-ray diffraction data. Further structure refinement was carried out by means of Jana2006 software package using anharmonic ADP for La1 and Zn atoms.Anharmonic displacement parameters for other atoms were not refined because in case of their refinement their standard deviations were larger than obtained values. As the result we gained lower absolute values of peak and hole in the difference Fourier map (1.02 and -1.17 e Å -3 respectively). The resulting isosurface drawn at the level 0.308 e/Å 3 and sections of difference Fourier map are given in Fig. 2. These maps and sections are noisy but some trends in location of positive and negative regions can be noticed. Positive residual electron density is mostly situated around zinc atoms and near layers made of tin atoms. Negative residual density is mostly located between lanthanum atoms which means that lanthanum atoms donate their electrons to zinc and tin atoms. Similar behaviour of lanthanum atoms can be observed in the LaZn 12.37 compound using electronic structure calculations (See Oshchapovsky et al., (2011)). As a conclusion this compound besides dominate metallic bonding has a weak ionic interaction between lanthanum and zinc and tin atoms. S2. ExperimentalSmall good quality single-crystal of title compound was isolated from alloy with composition La 7 ZnSn 2 during systematic investigation of lanthanum-rich region of La-Zn-Sn ternary system. The samples with high lanthanum contents were prepared by melting of pieces of pure metals in evacuated quartz ampoule with subsequent annealing at

Lanthanum tetrazinc, LaZn4

“…The main reason for such similarity is that the La atoms in LaZn 12.37 , LaZn 5 and LaZn 4 have large first coordination spheres consisting of Zn atoms only. In these compounds, and also in La 5 Zn 2 Sn (Oshchapovsky, Pavlyuk, Dmytriv, Chumak & Ehrenberg, 2011), the less electronegative La atoms donate their electron density to the more electronegative Zn and Sn atoms. Therefore, bonds between La and Zn/Sn atoms are mostly metallic but with some ionic component.…”

Redetermination of LaZn5based on single crystal X-ray diffraction data

“…LaZn 5 M r = 465.86 Hexagonal, P6=mmm a = 5.4654 (17) Å c = 4.2574 15 Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2006) and VESTA (Momma & Izumi, 2008); software used to prepare material for publication: publCIF (Westrip, 2010). This paper is part of a systematic investigation of binary RE-Zn (Oshchapovsky et al, 2011a;Zelinska et al, 2004) and ternary RE-Zn-M systems (where RE is a rare earth metal and M is a p-element of group IV) (Oshchapovsky et al, 2011b;Pavlyuk et al, 2009). The binary La-Zn system is not completely investigated yet (Berche et al, 2009), especially with respect to the structure of the compound LaZn 4 .…”

Investigation of the compound La5Zn2−xPb1 + x (x = 0.20–0.32)

“…DOS calculated for both structure models, have similar shapes (Figure) and show metallic bonding. Higher values of ELF around Zn and Pb in comparison to La atoms, and local minima at the DOS plots near Fermi level can indicate partial electron transfer from the La atoms to Zn, Pb and weak ionic bonding, which is typical for other related compounds [8,[11][12][13][14].…”