Nowotny phase

In inorganic chemistry, a Nowotny chimney ladder phase (NCL phase) is a particular intermetallic crystal structure found with certain binary compounds. NLC phases are generally tetragonal and are composed of two separate sublattices. The first is a tetragonal array of transition metal atoms, generally from group 4 through group 9 of the periodic table. Contained within this array of transition metal atoms is a second network of main group atoms, typically from group 13 (boron group) or group 14 (carbon group). The transition metal atoms form a chimney with helical zigzag chain. The main-group elements form a ladder spiraling inside the transition metal helix.

Cr₁₁Ge₁₉ crystals

Cr₁₁Ge₁₉ lattice structure

The phase is named after one of the early investigators H. Nowotny.^[1][2][3] Examples are RuGa₂, Mn₄Si₇, Ru₂Ge₃, Ir₃Ga₅, Ir₄Ge₅ V₁₇Ge₃₁, Cr₁₁Ge₁₉, Mn₁₁Si₁₉, Mn₁₅Si₂₆, Mo₉Ge₁₆, Mo₁₃Ge₂₃, Rh₁₀Ga₁₇, and Rh₁₇Ge₂₂.^[4]

In RuGa₂ the ruthenium atoms in the chimney are separated by 329 pm. The gallium atoms spiral around the Ru chimney with a Ga–Ga intrahelix distance of 257 pm. The view perpendicular to the chimney axis is that of a hexagonal lattice with gallium atoms occupying the vertices and ruthenium atoms occupying the center. Each gallium atom bonds to 5 other gallium atoms forming a distorted trigonal bipyramid. The gallium atoms carry a positive charge and the ruthenium atoms have a formal charge of −2 (filled 4d shell).^[5]

In Ru₂Sn₃ the ruthenium atoms spiral around the tin inner helix. In two dimension the Ru atoms form a tetragonal lattice with the tin atoms appearing as triangular units in the Ru channels.^[6]

The occurrence of a LCP phase can be predicted by the so-called 14 electron rule. In it the total number of valence electrons per transition metal atom is 14.^[7][8][9]

References

 

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1. Schwomma, O.; Preisinger, A.; Nowotny, H.; Wittmann, A. (1964). "Die Kristallstruktur von Mn₁₁Si₁₉ und deren Zusammenhang mit Disilicid-Typen". Monatshefte für Chemie und Verwandte Teile Anderer Wissenschaften. 95 (6): 1527–1537. doi:10.1007/BF00901708.
2. Schwomma, O.; Nowotny, H.; Wittmann, A. (1964). "Untersuchungen im System: Ru−Sn". Monatshefte für Chemie und Verwandte Teile Anderer Wissenschaften. 95 (6): 1538–1543. doi:10.1007/BF00901709.
3. Völlenkle, H.; Wittmann, A.; Nowotny, H. (1964). "Untersuchungen an Germaniden der Übergangsmetalle V, Cr, Mo und Mn". Monatshefte für Chemie und Verwandte Teile Anderer Wissenschaften. 95 (6): 1544–1549. doi:10.1007/BF00901710.
4. Lu, Guoxin; Lee, Stephen; Lin, Jianhua; You, Liping; Sun, Junliang; Schmidt, Joshua Teal (2002). "RuGa_vSn_w Nowotny Chimney Ladder Phases and the 14-Electron Rule". Journal of Solid State Chemistry. 164 (2): 210–219. Bibcode:2002JSSCh.164..210L. doi:10.1006/jssc.2001.9462.
5. King, R. Bruce (2007). "The Relationship between the Nowotny Chimney Ladder". Revista de Chimie. 58 (5): 439–441.
6. Fredrickson, Daniel C.; Lee, Stephen; Hoffmann, Roald; Lin, Jianhua (2004). "The Nowotny Chimney Ladder Phases: Following thecpseudo Clue toward an Explanation of the 14 Electron Rule". Inorganic Chemistry. 43 (20): 6151–6158. doi:10.1021/ic049427n. PMID 15446859.
7. Jeitschko, W.; Parthé, E. (1967). "The crystal structure of Rh₁₇Ga₂₂, an example of a new kind of electron compound". Acta Crystallographica. 22 (3): 417–430. doi:10.1107/S0365110X67000799.
8. Pearson, W. B. (1970). "Phases with Nowotny chimney-ladder structures considered as 'electron' phases". Acta Crystallographica Section B. 26 (7): 1044–1046. doi:10.1107/S0567740870003564.
9. Fredrickson, Daniel C.; Lee, Stephen; Hoffmann, Roald (2004). "The Nowotny Chimney Ladder Phases: Whence the 14 Electron Rule?". Inorganic Chemistry. 43 (20): 6159–6167. doi:10.1021/ic049897h. PMID 15446860.