J. Phys. I France
Volume 6, Numéro 12, December 1996
Page(s) 1527 - 1553
DOI: 10.1051/jp1:1996172
J. Phys. I France 6 (1996) 1527-1553

Electronic Structure of the $\mathsf{\alpha}$-(BEDT-TTF) $\mathsf{_2}$MHg(XCN) $\mathsf{_4}$ (M = Tl, K, NH $\mathsf{_4}$; X = S, Se) and Related Phases. Synthesis and Crystal Structure of the New Stable Organic Metal $\alpha$-(BEDT-TTF) $\mathsf{_2}$TlHg(Se $\mathsf{_{\rm 1-x}}$S $\mathsf{_{\rm x}}$CN) $\mathsf{_4}$ (x = 0.125)

R. Rousseau1, M.-L. Doublet2, E. Canadell1, 2, R.P. Shibaeva3, S.S. Khasanov3, L.P. Rozenberg3, N.D. Kushch4 and E.B. Yagubskii4

1  Institut de Ciència de Materials de Barcelona (CSIC), Campus de la UAB, 08193 Bellaterra, Spain
2  Laboratoire de Structure et Dynamique des Systèmes Moléculaires et Solides, Université de Montpellier II, 34095 Montpellier Cedex, France
3  Institut of Solid State Physics, Russian Academy of Sciences, Chernogolovka MD, 142432 Russia
4  Institut of Chemical Physics at Chernogolovka, Russian Academy of Sciences, Chernogolovka MD, 142432 Russia

(Received 8 April 1996, accepted 1 July 1996)

The synthesis, crystal structure, conductivity and electronic band structure of the new molecular metal $\alpha$-(BEDT-TTF) 2 TlHg (Se 1-xS xCN) 4 ( x=0.125) are reported. $\alpha$-(BEDT-TTF) 2TlHg(Se 1-xS xCN) 4( x=0.125) is isostructural with all other members of the family of $\alpha$-(BEDT-TTF) 2MHg(XCN) 4 salts and is a stable metal down to very low temperatures. A general study of the electronic structure of all structurally characterized $\alpha$-(BEDT-TTF) 2MHg(XCN) 4 salts as well as $\alpha$-(BEDT-TTF) 2I 3, $\alpha$-(BEDT-TTF) 2IBr 2 and $\alpha$-(BEDT-TTF) 4PtBr 6 is also reported. Different aspects related to the electronic structure of these salts like the stability of the metallic state and the nature of the Fermi surface are discussed and correlated with the details of their crystal structures. The origin of the different dimensionality of the carriers for the $\alpha$-(BEDT-TTF) 2MHg(XCN) 4 salts (i.e., 1D electrons but 2D holes), the metal to insulator transition in $\alpha$-(BEDT-TTF) 2I 3 and the semiconducting behavior of $\alpha$-(BEDT-TTF) 2IBr 2 and $\alpha$-(BEDT-TTF) 4PtBr 6 are also discussed.

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