Tin–Selenium Compounds at Ambient and High Pressures

Abstract

SnxSey crystalline compounds consisting of Sn and Se atoms of varying composition are systematically investigated at pressures from 0 to 100 GPa using the first-principles evolutionary crystal structure search method based on density functional theory (DFT). All known experimental phases of SnSe and SnSe2 are found without any prior input. A second order polymorphic phase transition from SnSe-P nma phase to SnSe-Cmcm phase is predicted at 2.5 GPa. Initially being semiconducting, this phase becomes metallic at 7.3 GPa. Upon further increase of pressure up to 36.6 GPa, SnSe-Cmcm phase is transformed to CsCl-type SnSe-P m 3m phase, which remains stable at even higher pressures. A metallic compound with different stoichiometry, Sn3Se4-I 43d, is found to be thermodynamically stable from 18 GPa to 70 GPa. Known semiconductor tin diselenide SnSe2-P 3m1 phase is found to be thermodynamically stable from ambient pressure up to 18 GPa. Initially being semiconducting, it experiences metalization at pressures above 8 GPa.

Effects of temperature and pressure on the optical and vibrational properties of thermoelectric SnSe

“…1) [19,[23][24][25]. For the sake of completeness, we mention that further compression leads SnSe towards a metallic CsCl-type structure between 30-40 GPa [26,27]. Given that the high-temperature and (first) high-pressure modification of SnSe have the same space group, it was proposed that pressure can effectively lower the P nma → Bbmm transition temperature [10, 11, 15-19, 25, 28].…”

Pressure‐Induced Metallization and Robust Superconductivity in Pristine 1T‐SnSe2

“…Around the critical point, the n e is enhanced to ≈10 19 cm −3 , concomitant with remarkable drop of resistance at 250 K from ≈100 Ω at ambient pressure to ≈1 Ω (see the inset of Figure 4). [26,27] However, the results of synchrotron XRD show the structure of 1T-SnSe 2 seems to be stable up to 46.0 GPa (see Figure 2). On the other hand, the superconducting onset transition temperature T c increases rapidly and remains a nearly constant value of ≈6.1 K between 30.1 and 50.3 GPa, which indicates the robust superconductivity under high pressure.…”

“…[23][24][25] The structural and physical properties of SnSe 2 under high pressure have been recently investigated by theoretical calculations, [26,27] while the experimental investigation is still lacking. [23][24][25] The structural and physical properties of SnSe 2 under high pressure have been recently investigated by theoretical calculations, [26,27] while the experimental investigation is still lacking.…”

“…Yu et al theoretically predicted that SnSe 2 transforms into the hexagonal R-3m phase at 5 GPa, and becomes thermodynamically unstable to spontaneously decompose into Sn 3 Se 4 and Se at 20 GPa. [27] Here, we report the structural and conductivity properties of pristine 1T-SnSe 2 under high pressure by combining synchrotron X-ray diffraction (XRD) and electrical transport experiments. [26] In addition, Nguyen-Cong et al theoretically suggest that the hexagonal P-3m1 SnSe 2 phase is thermodynamically stable up to 18 GPa and experiences metallization above 8 GPa, concomitant with a similar decomposition at 30.0 GPa.…”

“…[28] Considering only the z position of the Se atoms is variable in this 1T structure, the standard Le Bail method was used for the refinement www.advelectronicmat.de via the general structure analysis system (GSAS) program. [26,27] One can see that upon compression from ambient pressure to 46.0 GPa, the parameter c and a decrease by ≈17.0% and 5.6%, respectively, revealing large anisotropy of axial compressibility due to the quasi-2D nature of the lattice. The refined lattice parameter a, c, and axis ratio c/a are displayed together in Figure 2b.…”