Weblink 9.6 The structures of solid CaSi₂ and K₄Si₄

The structures of CaSi₂ (with calcium coloured grey and silicon blue) and K₄Si₄ (with potassium grey and silicon blue).

The Si atoms in CaSi₂ form an arrangement similar to that seen in a-arsenic (Fig. 8.23 on page 282), with layers of Ca²⁺ ions sandwiched in between the layers of Si.

In  K₄Si₄, the Si^- ions form tetrahedral units, Si₄^4-, which are isoelectronic with the P₄ units in the structure of white phosphorus (Fig. 1.17 on page 25).

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