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Electronic Structures of Ln 3+ α‐SiAIONs with Correlations to Solubility and Solution Effects
Author(s) -
Nakayasu Tetsuo,
Yamada Tetsuo,
Tanaka Isao,
Adachi Hirohiko,
Goto Seichi
Publication year - 1996
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1996.tb09011.x
Subject(s) - antibonding molecular orbital , ionic radius , lanthanide , chemistry , atomic orbital , ionic bonding , solubility , population , ion , crystallography , cluster (spacecraft) , covalent bond , physics , electron , demography , organic chemistry , quantum mechanics , sociology , computer science , programming language
First‐principles molecular‐orbital calculations using the discrete‐variational Xα method have been made on model clusters of α‐Si 3 N 4 and its solid solutions with lanthanide elements, which occupy interstitial sites in the structure. The formula is Ln χ Si 12–4.5χ Al 4.5χ O 1.5χ N16–1.5χ (Ln = La, Nd, Gd, Dy, Ho, Er, Tm, Yb), i.e., a Ln‐α‐SiAION solid solution. Covalent bond strength between Si and N, evaluated by overlap population, increases because of the presence of trivalent charges at the interstitial sites. When a Ln 3+ ion is present, antibondings occur between Ln orbitals and N/Si orbitals, and they depend significantly on the ionic radius of Ln 3+ . The total overlap population for the whole cluster is determined by the balance of Si‐N bond reinforcement and Ln‐N/Si antibonding. Although no lattice relaxation around the Ln 3+ ion is included in the present calculation, good correlation between maximum solubility and the total overlap population for the whole cluster is demonstrated for the first time.