Abstract
hbox {MoSe}_2 is a layered transition-metal dichalcogenide (TMD) with outstanding electronic and optical properties, which is widely used in field-effect transistor (FET). Here the structural evolution and phase transition of hbox {MoSe}_2 under high pressure are systematically studied by CALYPSO structural search method and first-principles calculations. The structural evolutions of hbox {MoSe}_2 show that the ground state structure under ambient pressure is the experimentally observed P6_3/mmc phase, which transfers to R3m phase at 1.9 GPa. The trigonal R3m phase of hbox {MoSe}_2 is stable up to 72.1 GPa, then, it transforms into a new P6_3/mmc phase with different atomic coordinates of Se atoms. This phase is extremely robust under ultrahigh pressure and finally changes to another trigonal R-3m phase under 491.1 GPa. The elastic constants and phonon dispersion curves indicate that the ambient pressure phase and three new high-pressure phases are all stable. The electronic band structure and projected density of states analyses reveal a pressure induced semiconducting to metallic transition under 72.1 GPa. These results offer a detailed structural evolution and phase diagram of hbox {MoSe}_2 under high pressure, which may also provide insights for exploration other TMDs under ultrahigh pressure.
Highlights
MoSe2 is a layered transition-metal dichalcogenide (TMD) with outstanding electronic and optical properties, which is widely used in field-effect transistor (FET)
The total energies and electronic properties are calculated within the density functional theory (DFT) framework, as it has implemented by Vienna ab initio simulation package (VASP) c ode[23]
We have successfully identified the experiment observed P63/mmc (2H) phase under ambient pressure, which verifies that the Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) method is perfectly suitable for MoSe2 and the searched results are reliable
Summary
MoSe2 is a layered transition-metal dichalcogenide (TMD) with outstanding electronic and optical properties, which is widely used in field-effect transistor (FET). The structural evolutions of MoSe2 show that the ground state structure under ambient pressure is the experimentally observed P63/mmc phase, which transfers to R3m phase at 1.9 GPa. The trigonal R3m phase of MoSe2 is stable up to 72.1 GPa, it transforms into a new P63/mmc phase with different atomic coordinates of Se atoms. Our results show that MoSe2 transfers from P63/mmc structure to R3m phase at 1.9 GPa, which is stable up to 72.1 GPa. Interestingly, as the pressure increase, MoSe2 again transfers from R3m phase to P63/mmc, it is metallic, which is different from the semiconducting P63/mmc phase under ambient pressure. As the pressure increase, MoSe2 again transfers from R3m phase to P63/mmc, it is metallic, which is different from the semiconducting P63/mmc phase under ambient pressure These results are different from the previous experiments showed that MoSe2 is mostly stable as 2Hc phase below 100 GPa11,12. To further explore the new phases and structural transition sequence of MoSe2 under high pressure, especially at ultrahigh pressure
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