Nowotny phase

A Nowotny chimney ladder phase (NCL phase) in inorganic chemistry 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 around the transition metal helix.

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

1. ^ Die Kristallstruktur von Mn11Si19 und deren Zusammenhang mit Disilicid-Typen O. Schwomma, A. Preisinger, H. Nowotny and A. Wittmann Monatshefte für Chemie / Chemical Monthly, 1964, Volume 95, Number 6, Pages 1527-1537 doi: 10.1007/BF00901708
2. ^ Untersuchungen im System: Ru−Sn O. Schwomma, H. Nowotny and A. Wittmann Monatshefte für Chemie / Chemical Monthly Volume 95, Number 6, 1538-1543, doi:10.1007/BF00901709
3. ^ Untersuchungen an Germaniden der Übergangsmetalle V, Cr, Mo und Mn H. Völlenkle, A. Wittmann and H. Nowotny Monatshefte für Chemie / Chemical Monthly Volume 95, Number 6, 1544-1549, doi:10.1007/BF00901710
4. ^ RuGa_vSnw Nowotn_y Chimney Ladder Phases and the 14-Electron Rule Guoxin Lu, Stephen Leeb, Jianhua Lin, Liping You, Junliang Sun and Joshua Teal Schmidt Journal of Solid State Chemistry Volume 164, Issue 2, 1 March 2002, Pages 210-219 doi:10.1006/jssc.2001.9462
5. ^ The Relationship between the Nowotny Chimney Ladder Solid State Phases and Metal-Phosphorus Wheels R. BRUCE KING REV. CHIM. 58 Nr. 5 2007
6. ^ The Nowotny Chimney Ladder Phases: Following the cpseudo Clue toward an Explanation of the 14 Electron Rule Daniel C. Fredrickson, Stephen Lee, Roald Hoffmann, and Jianhua Lin Inorg. Chem., 2004, 43 (20), pp 6151–6158 doi:10.1021/ic049427n
7. ^ The crystal structure of Rh17Ga22, an example of a new kind of electron compound W. Jeitschko and E. Parthé Acta Cryst. (1967). 22, 417-430 doi:10.1107/S0365110X67000799
8. ^ Phases with Nowotny chimney-ladder structures considered as `electron' phases W. B. Pearson Acta Cryst. (1970). B26, 1044-1046 doi:10.1107/S0567740870003564
9. ^ The Nowotny Chimney Ladder Phases: Whence the 14 Electron Rule? Daniel C. Fredrickson, Stephen Lee, and Roald Hoffmann Inorg. Chem., 2004, 43 (20), pp 6159–6167 doi:10.1021/ic049897h