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Calculation of the Electronic Structure of sp Elements in β‐Si 3 N 4 with Correlation to Solubility and Solution Effects
Author(s) -
Tanaka Isao,
Niihara Koichi,
Nasu Saburo,
Adachi Hirohiko
Publication year - 1993
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.1151-2916.1993.tb04024.x
Subject(s) - electronegativity , ionic radius , solubility , chemistry , thermodynamics , electronic structure , atom (system on chip) , ionic bonding , atomic radius , population , cluster (spacecraft) , electronic correlation , dopant , computational chemistry , doping , ion , condensed matter physics , molecule , physics , demography , organic chemistry , sociology , computer science , programming language , embedded system
Local electronic structures around the sp ‐element solutes in β‐Si 3 N 4 have been examined from first principles by the discrete‐variational (DV) Xα method for the first time. A solute atom, M, was put substitutionally into the Si sites of a (Si 3 N 10 ) 18‐ cluster, and Hartree–Fock–Slater equations were solved self‐consistently. The relationship between the calculated overlap population of electrons between the solute and nitrogen and the experimental solubility and the magnitude of the solution effects was examined, and a satisfactory correlation was found. Based on the present calculations, the Sp ‐element solutes are classified into the following three categories: (1) Elements such as K, Ca, Na, and Mg are almost insoluble and localize at the intergranular glassy phase or precipitates. (2) Remarkable solution effects to lose the local covalency are expected for Li, Be, Ga, and Al. They may enhance the volume diffusivity and also decrease the elastic constants considerably. (3) For B, C, and Ge, no significant reduction in local covalency is expected when they dissolve. The correlations between the calculated overlap population and empirical ionic radii of solute atoms and Pauling's electronegativity were found to be weak, indicating that these empirical parameters are not sufficient to represent the electronic structure change due to the substitution and hence solubility and solution effects, although they are useful in describing general trends.