Book of Abstracts Book of Abstracts - Universität Konstanz

30
Novel elongated Chevrel-type (Mo3S3)nS2 clusters
Gotthard Seifert and Sibylle Gemming
Institut f. Physikalische Chemie, Technische UniversitätDresden, D-01062 Dresden, Germany
Clusters of the composition Mo3nS3n+2 can be regarded as building blocks of the
corresponding sulfur-based Chevrel phases [1]. These compounds are generally built from equal
amounts of two Mo3nS3n+2 species with different values of n, thus the overall formula unit of the
network is Mo3nS3n+4. For the alkali metals as counter ions the charge state of the single cluster
building block is -1. Thus, the clusters in these compounds occur in the same charge state as the
free clusters recently observed by experimental studies [2].
The cluster series up to n = 9 was investigated by density-functional-based calculations. Both
the neutral and the anionic species were investigated. All structures up to Mo21S23 exhibit a
HOMO-LUMO gap of about 0.5 eV. The relative stability of the neutral clusters shows a weak
even-odd-alternation, which roughly correlates with the HOMO-LUMO spacings. The relative
stabilities of the different members of the cluster sequence are highly dependent on the charge
state, i.e. on the number and type of counter ions in a solid phase. For comparison the infinitely
long [Mo6S6] n chain was investigated by DFT band structure calculations, employing periodic
boundary conditions.
Calculated I-V curves fur such clusters show that the quasi one-dimensional Chevrel-type
structures are promising candidates for nanoelectronic devices.
Figure 1. Chevrel type structures of the Mo6S8 , Mo9S11 , Mo18S20 clusters and part of an infinite chain of a Chevrel
structure (left to right, black Mo atoms ).
References
[1] D. Salloum, R. Gautier, P. Gougeon, M. Potel, J. Solid. State Chem. 177, 1672 (2004).
[2] N. Bertram , Y.D. Kim, G. Ganteför, to be published