Structural variations in Gd5Si4-xSnx: size vs. electronic effects

Abstract X-ray single crystal diffraction studies on the Gd 5 Si 4x Sn x series with 0 ≤ x ≤ 3 revealed an increase in the interslab T — T ( T = Si, Sn) dimer distances and transition from Gd 5 Si 4 -type structures for 0 ≤ x ≤ 1.5 ( d T—T = 2.49–2.71 Å) to the Pu 5 Rh 4 -type structure for x = 2 ( d T—T = 3.04 Å). The Ti 5 Ga 4 -type structure, which is a stuffed version of the hexagonal Mn 5 Si 3 structure, was observed for the Gd 5 SiSn 3 sample ( x = 3). Tight-binding linear-muffin-tin-orbital (TB-LMTO) calculations on Gd 5 Si 2 Sn 2 show that the interslab ( T 1— T 1) dimer stretching and the structural transition from the Gd 5 Si 4 -type to the Pu 5 Rh 4 -type results from the influence of the 5 p atomic orbital energy and the larger size of the Sn atoms on the electronic structure, as compared to the Si and Ge atoms in Gd 5 Si 4 and Gd 5 Si 2 Ge 2 .