Insulator-metal transition of highly compressed carbon disulfide

Ranga P. Dias, Choong-Shik Yoo, Minseob Kim, and John S. Tse

Phys. Rev. B 84, 144104 – Published 7 October 2011

Abstract

We present integrated spectral, structural, resistance, and theoretical evidences for simple molecular CS $_{2}$ transformations to an insulating black polymer with threefold carbon atoms at 9 GPa, then to a semiconducting polymer above 30 GPa, and finally to a metallic solid above 50 GPa. The metallic phase is a highly disordered three-dimensional network structure with fourfold carbon atoms at the carbon-sulfur distance of ∼1.70 Å. Based on first-principles calculations, we present two plausible structures for the metallic phase: α-chalcopyrite and tridymite, both of which exhibit metallic ground states and disordered diffraction features similar to that measured. We also present the phase and chemical transformation diagram for carbon disulfide, showing a large stability field of the metallic phase to 100 GPa and 800 K.

Received 24 August 2011

DOI:https://doi.org/10.1103/PhysRevB.84.144104

Authors & Affiliations

Ranga P. Dias¹, Choong-Shik Yoo^1,*, Minseob Kim¹, and John S. Tse²

¹Institute for Shock Physics, Department of Chemistry and Department of Physics, Washington State University, Pullman, Washington 99164, USA
²Department of Physics and Engineering Physics, University of Saskatchewan, Saskatchewan, Canada, S7N 5E2

^*csyoo@wsu.edu

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Vol. 84, Iss. 14 — 1 October 2011

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Images

Figure 1
Microphotographs of carbon disulfide under high pressure showing its transformation from (a) transparent fluid to (b) and (c) molecular solid (Cmca) at ∼1 GPa, to (d), (e), and (g) black polymer above 10 GPa ((-S-(C=S)-) $_{p}$ or CS3) and eventually to (f) and (h) a highly reflecting extended solid above 48 GPa (CS4) at ambient temperature. The rightmost image (h) illustrates the metallic reflectivity of CS $_{2}$ samples above 55 GPa similar to those of Platinum (Pt) metal probes in a four-probe configuration for resistance measurements.Reuse & Permissions
Figure 2
Pressure-induced Raman and electric resistance changes of carbon disulfide, showing the structural and electronic transitions. The inset shows subtle changes in Raman spectra in the 300–700 cm $^{- 1}$ region associated with the structural phase transitions at 10 and 30 GPa. The open and closed symbols signify, respectively, the data taken during the pressure uploading and downloading.Reuse & Permissions
Figure 3
(Left) The background-removed structural factor S(Q) and radial distribution function G(r) (inset) of carbon disulfide obtained at several high pressures, showing the pressure-induced structural changes. (Right) The calculated structure factors of α-chalcopyrite (I-42d, top) and α-tridymite ( $P 2_{1}$ 2 $_{1}$ 2 $_{1}$ , bottom), showing the two major features centered around 2.8 Å $^{- 1}$ and 4.9 Å $^{- 1}$ as observed in the experiments.Reuse & Permissions
Figure 4
The phase and chemical transformation diagram of carbon disulfide, showing the structural phase transitions, insulator-to-metal transition, and chemical decomposition. Open circles signify data from the present study. The present high-temperature experiments confirm the stability of CS3 phase to 710 K at 22 GPa and at least 725 K at 50 GPa, which define the decomposition line of carbon disulfide to carbon and sulfur.Reuse & Permissions
Figure 5
The Raman spectra of ohmically heated carbon disulfide, showing thermal decomposition of CS $_{2}$ to carbon and sulfur (phase VI) at around 720 K at 22 GPa (a) but no apparent decomposition at 50 GPa to the maximum temperature of 723 K (b). The laser-heated carbon disulfide, on the other hand, decomposes to carbon and sulfur (phase III) at 30 GPa and >1000 K (c).Reuse & Permissions
Figure 6
(a) The calculated enthalpies for the chalcopyrite (I-42d) and tridymite ( $P 2_{1}$ 2 $_{1}$ 2 $_{1}$ ) structure of CS $_{2}$ over a large pressure range from 20 to 60 GPa, showing that the chalcopyrite structure is more stable by about 0.3–0.4 eV/formula unit. (b) The electronic band structure of the chalcopyrite showing a metallic ground state. (c) The electronic band structure of the tridymite structure at 47 GPa, showing the metallic nature and flat and parallel bands. (d) The phonon band structure and density of state for the chalcopyrite structure, showing the major Raman-active A1 phonon mode at 500 cm $^{- 1}$ and other ir modes at 700–800 cm $^{- 1}$ .Reuse & Permissions

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