Compression of Silver Sulfide: X-ray Diffraction Measurements and Total-Energy Calculations

Abstract

Angle-dispersive X-ray diffraction measurements have been performed in acanthite, Ag(2)S, up to 18 GPa in order to investigate its high-pressure structural behavior. They have been complemented by ab initio electronic structure calculations. From our experimental data, we have determined that two different high-pressure phase transitions take place at 5 and 10.5 GPa. The first pressure-induced transition is from the initial anti-PbCl(2)-like monoclinic structure (space group P2(1)/n) to an orthorhombic Ag(2)Se-type structure (space group P2(1)2(1)2(1)). The compressibility of the lattice parameters and the equation of state of both phases have been determined. A second phase transition to a P2(1)/n phase has been found, which is a slight modification of the low-pressure structure (Co(2)Si-related structure). The initial monoclinic phase was fully recovered after decompression. Density functional and, in particular, GGA+U calculations present an overall good agreement with the experimental results in terms of the high-pressure sequence, cell parameters, and their evolution with pressure.

Electronic Topological Transition in Ag2Te at High-pressure

“…In particular, pressure is critical to the formation of topological superconductors1718192021. Moreover, it is obvious that the pressure-induced phase transition sequences for silver chalcogenides are very different222324. For Ag 2 S22, it experiences a phase transition sequence: P 2 1 / n  →  P 2 1 2 1 2 1  →  P 2 1 / n .…”

“…Moreover, it is obvious that the pressure-induced phase transition sequences for silver chalcogenides are very different222324. For Ag 2 S22, it experiences a phase transition sequence: P 2 1 / n  →  P 2 1 2 1 2 1  →  P 2 1 / n . For Ag 2 Se23, it undergoes structural changes: P 2 1 2 1 2 1  →  Pnma  →  Cmcm .…”

Impurity level evolution and majority carrier-type inversion of Ag2S under extreme compression: Experimental and theoretical approaches

“…Under ambient conditions, the electrical resistivity (q), Hall coefficient (R H ), carrier concentration (n), and mobility (l) are 0.22 XÁcm, À9.63 cm 3 C À1 , 6.98 Â 10 18 cm À3 , and 407.3 cm 2 V À1 s À1 , respectively. During compression, q, R H , n, and l all show discontinuous changes at 3.8 GPa and 7.8 GPa, according with the XRD measurement, 22 which has proved that Ag 2 S underwent a structural phase transition sequence of LP-HP1-HP2. For convenience, the anti-PbCl 2 -like, Ag 2 Se-type and Co 2 Sirelated phases are referred as the LP, HP1, and HP2 phases, respectively.…”

“…[19][20][21] The structure and related electrical properties of Ag 2 S have been extensively studied as a function of temperature at atmospheric conditions but insufficiently as a function of elevated pressure. Recently, David et al 22 used the roomtemperature angle dispersive x-ray diffraction (ADXRD) measurements up to 18 GPa to determine that Ag 2 S underwent two different high-pressure phase transitions at 5.0 and 10.5 GPa, respectively. The first was from an initial monoclinic anti-PbCl 2 -like structure (space group P2 1 /n) to an orthorhombic Ag 2 Se-type structure (space group P2 1 2 1 2 1 ).…”

“…The second was from P2 1 2 1 2 1 structure to a slight modified anti-PbCl 2 -like structure (Co 2 Si-related structure). Additionally, David et al 22 used the ab initio calculations to predict that the second high-pressure structure could transform to a Pnma structure at a higher pressure. However, whether the structural phase transitions can induce unusual changes in electrical transport parameters is still unknown.…”