TY  - JOUR
AU  - Zimmer, Dominik
AU  - Ruiz-Fuertes, J.
AU  - Morgenroth, W.
AU  - Friedrich, Alexandra
AU  - Bayarjargal, L.
AU  - Haussühl, E.
AU  - Santamaría-Pérez, D.
AU  - Frischkorn, S.
AU  - Milman, V.
AU  - Winkler, B.
TI  - Pressure-induced changes of the structure and properties of monoclinic α-chalcocite Cu<sub>2</sub>S
JO  - Physical review / B
VL  - 97
IS  - 13
SN  - 2469-9950
CY  - Woodbury, NY
PB  - APS
M1  - PUBDB-2018-02407
SP  - 134111
PY  - 2018
AB  - The high-pressure behavior of monoclinic (P2<sub>1</sub>/c)α-chalcocite, Cu<sub>2</sub>S, was investigated at ambient temperature by single-crystal x-ray diffraction, electrical resistance measurements, and optical absorption spectroscopy up to 16 GPa. The experiments were complemented by density-functional-theory-based calculations. Single-crystal x-ray diffraction data show that monoclinic α-chalcocite undergoes two pressure-induced first-order phase transitions at ∼3.1 and ∼7.1 GPa. The crystal structure of the first high-pressure polymorph, HP1, was solved and refined in space group P2<sub>1</sub>/c with a=10.312(4)Å, b=6.737(3)Å, c=7.305(1)Å, and β=100.17(2)∘ at 6.2(3) GPa. The crystal structure of the second high-pressure polymorph, HP2, was solved and refined in space group P2<sub>1</sub>/c with a=6.731(4)Å, b=6.689(2)Å, c=6.967(8)Å, and β=93.18(3)∘ at 7.9(4) GPa. Electrical resistance measurements upon compression and optical absorption experiments upon decompression show that the structural changes in α-chalcocite are accompanied by changes of the electrical and optical properties. Upon pressure release, the band gap Eg of α-chalcocite (1.24 eV at ambient conditions) widens across the first structural phase transition, going from 1.24 eV at 2.2 GPa (α-chalcocite) to 1.35 eV at 2.6 GPa (HP1), and closes significantly across the second phase transition, going from 1.32 eV at 4.4 GPa (HP1) to 0.87 eV at 4.9 GPa (HP2). The electrical resistance shows similar behavior: its highest value is for the first high-pressure polymorph (HP1), and its lowest value is for the second high-pressure polymorph (HP2) of α-chalcocite. These results are interpreted on the basis of calculated electronic band structures.  
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000429929800002
DO  - DOI:10.1103/PhysRevB.97.134111
UR  - https://bib-pubdb1.desy.de/record/407129
ER  -