Ce 4 (P 1-x Si x ) 3-z : A First Example for the Stabilization of the Anti-Th 3 P 4 Type Structure by Substitution in the Non-Metal Substructure Pavel S. Chizhov,* ,†,‡ Nellie R. Khasanova, † Michael Baitinger, ‡ Walter Schnelle, ‡ Yuri Prots, ‡ Ulrich Burkhardt, ‡ Evgeny V. Antipov, † and Yuri Grin ‡ Chemistry Department, Moscow State UniVersity, 119992 Moscow, Russia, and Max-Planck-Institut fu ¨r Chemische Physik fester Stoffe, No ¨thnitzer Str. 40, 01187 Dresden, Germany Received April 28, 2006 A first rare-earth phosphide silicide Ce 4 (P 1-x Si x ) 3-z and its analogues with La, Pr, and Nd were synthesized and characterized. The compounds crystallize in the anti-Th 3 P 4 structure type. The cerium compound shows a mixed occupation of the 12a site with Si and P and possesses a wide homogeneity range with respect to x and z variation. The electronic configuration of Ce, deduced from magnetic susceptibility and X-ray absorption spectroscopy data, remains 4f 1 (Ce 3+ ) independently from x and z. The cerium valence and the phase stability region are discussed employing electronic band-structure calculation and chemical bonding analysis with electron localization function. Atomic interactions are shown to remain nearly unchanged, while the change of the excess electron concentration with P/Si substitution is considered to play the main role for the stabilization of the structural motif. Introduction Rare-earth pnictides Ln 4 Pn 3 (Ln ) rare-earth metal; Pn ) P, As, Sb, Bi) raised great interest after the report about heavy fermion-like behavior of Yb 4 As 3 . 1 This compound has an anti-Th 3 P 4 type crystal structure with intermediate valence of Yb and low charge carrier concentration. The influence of the nature of pnictogen and of the rare-earth metal valence on the properties of Yb 4 Pn 3-z has been discussed in several reports. 2-5 Similar compounds with Eu were also investigated thoroughly, 6,7 but the origin of the unusual physical properties and the homogeneity ranges for Ln 4 P 3 phases are still under discussion. 8 The isostructural compounds of lanthanides other than Yb and Eu were not investigated in detail. Most of the RE 4 Pn 3 (RE ) rare-earth metal with the exception of Eu and Yb) compounds are stable with heavy pnictogens (Sb, Bi). 9 Only three analogous arsenides have been described up to now (La 4 As 3 , 9 Ce 4 As 3 , and Pr 4 As 3 ), 10 and no RE 4 P 3 phosphides were found. 11 However, the higher electronegativity of phosphor might lead to a different type of chemical interac- tion in comparison with As and Sb. This, in turn, may result in unusual physical and structural phenomena, for example, charge ordering. Moreover, the stabilization of RE 4 P 3 could provide new information about the valence state of lan- thanides and chemical bonding in compounds of this type. In the case of the phosphides RE 4 P 3 , assuming the oxidation state 3- of phosphor, the formal balance can be written as (RE 2+ ) 3 (RE 3+ ) 1 (P 3- ) 3 ; that is, only a part of the RE cations is required to be in the oxidation state 3+. For the RE elements with the unstable oxidation state 2+, this * To whom correspondence should be addressed. Tel.: +4935146464209. Fax: +4935146464002. E-mail address: chizhov@cpfs.mpg.de. † Moscow State University. ‡ Max-Planck-Institut fu ¨r Chemische Physik fester Stoffe. (1) Ochiai, A.; Suzuki, T.; Kasuya, T. J. Phys. Soc. Jpn. 1990, 59, 4129. (2) Ochiai, A.; Aoki, H.; Suzuki, T.; Helfrich, R.; Steglich, F. Physica B 1997, 230-232, 708. (3) Antonov, V. N.; Yaresko, A. N.; Perlov, A. Ya.; Thalmeier, P.; Fulde, P. Phys. ReV.B 1998, 58, 9752. (4) Staub, U.; Shi, M.; Schulze-Briese, C.; Patterson, B. D.; Fauth, F.; Dooryhee, E.; Soderholm, L.; Cross, J. O.; Mannix, D.; Ochiai, A. Phys. ReV.B 2005, 71, 075115. (5) Chichorek, T.; Aoki, H.; Gegenwart, P.; Lang, M.; Ochiai, A.; Steglich, F. Physica B 2002, 312-313, 370. (6) Cardoso, R.; Schnelle, W.; Grin, Yu.; von Schnering, H. G. Book of Abstracts, VIIth European Conference on Solid State Chemistry, Madrid, Sept 15-18, 1999; Vol. I, p 117. (7) Ochiai, A.; Shima, Y.; Shirakawa, M. Physica B 2002, 312-313, 362. (8) Burkhardt, U.; Grin, Yu.; von Schnering, H. G. Book of Abstracts, VIth European Conference of Solid State Chemistry, Zu ¨ rich, Sept 17- 20, 1997; PA124. (9) Hulliger, F.; Ott, H. R. J. Less-Common Met. 1977, 55, 103. (10) Ono, S.; Despault, J. G.; Calvert, L. D.; Taylor, J. B. J. Less-Common Met. 1970, 22, 51. (11) Kuz’ma, Yu.; Chykhrij, S. In Handbook of the Physics and Chemistry of Rare Earths; Gschneider, K. A., Jr., Eyring, L., Pecharsky, V. K., Eds.; Elsevier Science: New York, 1996; Vol. 23, Chapter 156, pp 285-427. Inorg. Chem. 2006, 45, 7210-7216 7210 Inorganic Chemistry, Vol. 45, No. 18, 2006 10.1021/ic060726h CCC: $33.50 © 2006 American Chemical Society Published on Web 08/05/2006