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New Rare‐Earth Metal Germanides RE 2 Ge 9 ( RE = Nd, Sm) by Thermal Decomposition of High‐Pressure Phases RE Ge 5
Author(s) -
Meier Katrin,
Wosylus Aron,
CardosoGil Raul,
Burkhardt Ulrich,
Curfs Caroline,
Hanfland Michael,
Grin Yuri,
Schwarz Ulrich
Publication year - 2012
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201200146
Subject(s) - germanium , orthorhombic crystal system , metastability , thermal decomposition , germanide , metal , crystallography , samarium , materials science , crystal structure , neodymium , chemistry , inorganic chemistry , silicon , metallurgy , physics , laser , organic chemistry , optics
The rare‐earth metal germanides RE 2 Ge 9 ( RE = Nd, Sm) have been prepared by thermal decomposition of the metastable high‐pressure phases RE Ge 5 at ambient pressure. The compounds adopt an orthorhombic unit cell with a = 396.34(4) pm; b = 954.05(8) pm and c = 1238.4(1) pm for Nd 2 Ge 9 and a = 395.46(7) pm; b = 946.4(2) pm and c = 1232.1(3) pm for Sm 2 Ge 9 . Crystal structure refinements reveal space group Pmmn (No. 59) for Nd 2 Ge 9 . The atomic pattern resembles an ordered defect variety of the pentagermanide motif RE Ge 5 ( RE = La; Nd, Sm, Gd, Tb) comprising corrugated germanium layers. These condense into a three‐dimensional network interconnected by eight‐coordinated germanium atoms. The resulting framework channels along [100] enclose the neodymium atoms. With respect to the atomic arrangement of the pentagermanides, half of the interlayer germanium atoms are eliminated in an ordered way so that occupied and empty germanium columns alternate along [001]. The rare‐earth metal atoms of both types of compounds, RE Ge 5 and RE 2 Ge 9 , exhibit the electronic states 4 f 3 and 4 f 5 (oxidation state +3) for neodymium and samarium, respectively, evidencing that the modification of the germanium network leaves the electron configuration of the metal atoms unaffected.