Manganese disilicide

Manganese disilicide (MnSi₂) is an intermetallic compound, a silicide of manganese. It is a non-stoichiometric compound, with a silicon deficiency expressed as MnSi_2–x. Crystal structures of many MnSi_2–x compounds resemble a chimney ladder and are called Nowotny phases. They include MnSi₂ (x=0), Mn₄Si₇ (x=0.250), Mn₁₁Si₁₉ (x=0.273), Mn₁₅Si₂₆ (x=0.267) and Mn₂₇Si₄₇ (x=0.259). These phases have very similar unit cells whose length varies from 1.75 nm for MnSi₂ or Mn₄Si₇, which have almost the same structures, to 11.8 nm for Mn₂₇Si₄₇.

MnSi_2–x Nowotny phases have a Mn sublattice with a β-tin structure overlaid with a face-centered cubic Si sublattice. They resemble chimneys of transition metal atoms containing spiraling ladders of Si. These phases are semiconductors with a band gap of 0.4 to 0.9 eV. They exhibit a reasonably high thermoelectric figure of merit ZT ~ 0.8 and have potential applications in thermoelectric generators.