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The high-pressure electronic structure of the [Ni(ptdt)2] organic molecular conductor

Tulip, P.R.; Bates, S.P.; Clark, S.J.

The high-pressure electronic structure of the [Ni(ptdt)2] organic molecular conductor Thumbnail


P.R. Tulip

S.P. Bates


The electronic structure of the single component molecular crystal [Ni(ptdt)2] (ptdt = propylenedithiotetrathiafulvalenedithiolate) is determined at ambient and high pressure using density functional theory. The electronic structure of this crystal is found to be of the “crossing bands” type with respect to the dispersion of the HOMO and LUMO, resulting in a small, non-zero density of states at the Fermi energy at ambient pressure, indicating that this crystal is a “poor quality” metal, and is consistent with the crystal's resistivity exhibiting a semiconductor-like temperature dependence. The ambient pressureband structure is found to be predominantly one-dimensional, reflecting enhanced intermolecular interactions along the [100] stacking direction. Our calculations indicate that the band structure becomes two-dimensional at high pressures and reveals the role of shortened intermolecular contacts in this phenomenon. The integrity of the molecular structure is found to be maintained up to at least 22 GPa. The electronic structure is found to exhibit a crossing bands nature up to 22 GPa, where enhanced intermolecular interactions increase the Brillouin zone centre HOMO-LUMO gap from 0.05 eV at ambient pressure to 0.15 eV at 22 GPa; this enhanced HOMO-LUMO interaction ensures that enhancement of a metallic state in this crystal cannot be simply achieved through the application of pressure, but rather requires some rearrangement of the molecular packing. Enhanced HOMO-LUMO interactions result in a small density of states at the Fermi energy for the high pressure window 19.8–22 GPa, and our calculations show that there is no change in the nature of the electronic structure at the Fermi energy for these pressures. We correspondingly find no evidence of an electronic semiconducting-metal insulator transition for these pressures, contrary to recent experimental evidence [Cui et al., J. Am. Chem. Soc.131, 6358 (2009)]10.1021/ja901553z.


Tulip, P., Bates, S., & Clark, S. (2012). The high-pressure electronic structure of the [Ni(ptdt)2] organic molecular conductor. The Journal of Chemical Physics, 137(2), Article 024701.

Journal Article Type Article
Acceptance Date Jun 12, 2012
Publication Date Jul 14, 2012
Deposit Date Jun 3, 2014
Publicly Available Date Aug 18, 2015
Journal Journal of Chemical Physics
Print ISSN 0021-9606
Electronic ISSN 1089-7690
Publisher American Institute of Physics
Peer Reviewed Peer Reviewed
Volume 137
Issue 2
Article Number 024701


Published Journal Article (1.4 Mb)

Copyright Statement
© 2012 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in The Journal of Chemical Physics 137, 024701 (2012) and may be found at

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