J. Phys. I France
Volume 6, Numéro 12, December 1996
Page(s) 1555 - 1565
DOI: 10.1051/jp1:1996173
J. Phys. I France 6 (1996) 1555-1565

Stable Molecular Metal [ Pd(dddt) $_{\bf 2}$] Ag $_{\bf 1.54}$Br $_{\bf 3.50}$: Synthesis, Crystal Structure, Transport Properties and Electronic Band Structure

L.A. Kushch1, S.V. Konovalikhin1, L.I. Buravov1, A.G. Khomenko1, G.V. Shilov1, K. Van2, O.A. Dyachenko1, E. B. Yagubskii1, C. Rovira3 and E. Canadell4, 5

1  Institute of Chemical Physics in Chernogolovka, Russian Academy of Sciences, Chernogolovka MD, 142432 Russia
2  Institute of Experimental Mineralogy, Russian Academy of Sciences, Chernogolovka MD, 142432 Russia
3  Deparament de Quìmica Física, Facultat de Quìmica, Universitat de Barcelona, 08028 Barcelona, Spain
4  Institut de Ciencia de Materials de Barcelona (CSIC), Campus de la UAB, 08193 Bellaterra, Spain
5  Laboratoire de Structure et Dynamique des Systèmes Moléculaires et Solides, Université de Montpellier II, 34095 Montpellier Cedex, France

(Received 5 March 1996, accepted 11 June 1996)

The synthesis, crystal and electronic band structures as well as conducting properties of the new stable molecular metal [ Pd(dddt) 2] Ag 1.54Br 3.50 (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolato) are reported. the crystal structure contains layers of donor cations alternating with layers of silver bromide complex anions along the a axis of the unit cell. The Ag and Br atoms are disordered in the anion layer. The conducting layers contain uniform stacks of the translationally equivalent Pd(dddt) 2 cations along the c-axis with a Pd ...Pd distance of 4.157(2) Å. Within the cation layers there are shortened interstack S ...S contacts (3.49(3) and 3.56(3) Å). The temperature dependence of the resistivity exhibits metallic behaviour down to 1.3 K. The resistivity anisotropy ( $\rho_a^*/\rho_{bc}$) at room temperature is about 600 and does not change considerably when decreasing the temperature down to 4.2 K. The origin of the metallic conductivity of [ Pd(dddt) 2] Ag 1.54Br 3.50 as well as the stability of this salt with respect to metal-to-insulator transitions is explained on the basis of tight binding band structure calculations.

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