The existence of edges and particularly of faces

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Unformatted text preview: static valency principle. (局部電荷或靜電鍵結強度之平衡)。 In a stable coordination structure, the total strength of the valency bonds (electrostatic bonds) that reach an anion from all neighboring bonds) cations is equal to the charge of the anion cations is equal to the charge of the anion. (a) Electrostatic bond strength = Electrostatic valency = z/ n = Ion’s valence charge/Coordination number (b) Localized neutralization of charge around an anion in an Localized ionic structure. 國立成功大學地球科學系 礦物學(一) 江威德 (c) The Verwey-Heilmann principle of maximal charge The Verweyneutralization neutralization. In In a stable ionic structure, the charge on any cation is neutralized by adjacent anions (first coordination neighbors). → A tendency for high-charge cations to have a large highcoordination number (occupying larger sites), but such cations are usually small and tend to occupy smaller sites. → A compromise between localized charge neutralization and effects of smaller ionic ratios. Maximal charge neutralization 國立成功大學地球科學系 礦物學(一) 江威德 礦物學(一)_江威德_Lecture 12 9 2009/11/24 Pauling’s Rules 國立成功大學地球科學系 NaCl Halite 岩鹽 CaF2 Fluorite 螢石 ZnS Sphalerite 閃鋅礦 國立成功大學地球科學系 礦物學(一) 江威德 The electrostatic valency principle Tetrahedral sheet Octahedral sheet Talc 滑石 Mg3Si4O10(OH)2 Half-cell formula formula T O T T O T T O T 礦物學(一)_江威德_Lecture 12 2 tetrahedral sheets (T) + Si4O10(OH)2 → Si8O20(OH)4 1 octahedral sheet (O) Mg6O8(OH)4 國立成功大學地球科學系 礦物學(一) 江威德 10 2009/11/24 Pauling’s Rules 國立成功大學地球科學系 Violation of the electrostatic valency principle [6]Al[5]Al[4]SiO 5 Andalusite 紅柱石 [5]Al [4]Si [5]Al [4]Si [5]Al [5]Al [4]Si [6]Al [5]Al [4]Si [6]Al [5]Al [6]Al [6]Al [4]Si [6]Al [6]Al [6]Al 國立成功大學地球科學系 礦物學(一) 江威德 Rule 3: The principle of polyhedral sharing. (...
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