Pressure-induced 1T to 3R structural phase transition in metallic VSe2 : X-ray diffraction and first-principles theory (original) (raw)
Related papers
Numerical simulation of structural, electronic and optical properties of vanadium diselenide (VSe2)
2017
VSe2 belongs to a group of compounds called transition metal dichalcogenides. This group of compounds have been exploited by several researchers both computationally and experimentally because of their intriguing properties such as low resistance, high chemical and mechanical stability and ease of synthesis. These properties make them candidates for various applications ranging from catalysis, electronics, aerospace engineering to plasmonics, just to mention a few. In this study we numerically simulated some of the properties of VSe2. In this regard, a structural study of VSe2 was undertaken using Density Functional Theory (DFT) with the Perdew-Burke-Ernzerhof (PBE) exchange correlation functional with two flavours of van der Waal’s interaction corrections namely Grimme (D2) and Tkatchenko-Scheffler (TS) to describe the inter-layer interactions of VSe2 accurately. From the structural data obtained, PBE+D2 describe the structural parameters of VSe2, when compared to experimental data...
Structural Phase Transition of Vanadium at 69 GPa
Physical Review Letters, 2007
A phase transition was observed at 63-69 GPa and room temperature in vanadium with synchrotron x-ray diffraction. The transition is characterized as a rhombohedral lattice distortion of the body-centeredcubic vanadium without a discontinuity in the pressure-volume data, thus representing a novel type of transition that has never been observed in elements. Instead of driven by the conventional s-d electronic transition mechanism, the phase transition could be associated with the softening of C 44 trigonal elasticity tensor that originates from the combination of Fermi surface nesting, band Jahn-Teller distortion, and electronic topological transition.
Pressure-Induced Valence Transitions in Rare Earth Chalcogenides and Pnictides
physica status solidi (b), 2001
The electronic structure of rare earth chalcogenides and pnictides is calculated with the ab-initio self-interaction corrected local-spin-density approximation (SIC-LSD). This approach allows both an atomic-like description of the rare earth f-electrons and an itinerant description of other electronic degrees of freedom. Specifically, different formal valencies of the rare earth atom, corresponding to different f-shell occupancies, can be studied and their energies compared, leading to a first-principles theory for pressure-induced valence transitions. SIC-LSD calculations for cerium monopnictides and monochalcogenides, Yb monochalcogenides, and EuS are presented. The observed equilibrium lattice constants are well reproduced assuming a trivalent Ce configuration and divalent Eu and Yb configurations. The trends in the high pressure behavior of these systems are discussed. With applied pressure, isostructural phase transitions are found to occur in CeP and CeS, caused by the delocalization of the Ce f-electron, while in the heavier Ce compounds, the structural B1 ! B2 transition happens before f-electron delocalization occurs. Similarly, both Eu and Yb chalcogenides transfer to trivalent configurations with pressure, in accordance with observation.
Theoretical confirmation of a high-pressure rhombohedral phase in vanadium metal
Physical Review B, 2007
Recent diamond-anvil-cell ͑DAC͒ experiments revealed a new phase in vanadium metal at high pressure. Here we present results from first-principles electronic-structure calculations confirming the existence of this phase. The structure corresponds to a rhombohedral distortion of the bcc ambient-pressure phase. The calculated transition pressure ͑0.84 Mbar͒ and density compare reasonably with the measured data. Interestingly, a reentrant bcc phase is discovered at ultrahigh pressures above 2.8 Mbar, close to the limit of DAC experimental capabilities. We show, extending prior work, that the phase transitions in vanadium are driven by subtle electronic-structure effects.
Strain engineering a 4a×√3a charge-density-wave phase in transition-metal dichalcogenide 1T−VSe2
Physical Review Materials, 2017
We report a rectangular charge density wave (CDW) phase in strained 1T-VSe 2 thin films synthesized by molecular beam epitaxy on c-sapphire substrates. The observed CDW structure exhibits an unconventional rectangular 4 √3 periodicity, as opposed to the previously reported hexagonal 4 4 structure in bulk crystals and exfoliated thin layered samples. Tunneling spectroscopy shows a strong modulation of the local density of states of the same 4 √3 CDW periodicity and an energy gap of 2 CDW 9.1 0.1 meV. The CDW energy gap evolves into a full gap at temperatures below 500 mK, indicating a transition to an insulating phase at ultra-low temperatures. Firstprinciples calculations confirm the stability of both 4 4 and 4 √3 structures arising from soft modes in the phonon dispersion. The unconventional structure becomes preferred in the presence of strain, in agreement with experimental findings.
Physical Review B
A new class of van der Waals heterostructures of (SnTe) m (Bi 2 Te 3) n (with m = 1, 2,. . and n = 1, 2,. .), consisting of a topological crystalline insulator SnTe and a topological insulator Bi 2 Te 3 are emerging with exciting properties and applications, such as in thermoelectrics. Our study examines the stability of these heterostructures (m = 1 and n = 1,2) under pressure using Raman scattering, synchrotron x-ray diffraction, and density functional theory. Raman studies as a function of pressure carried out at room temperature reveal a phase transition in the pressure regime of 3-5 GPa for both the compounds, which is shown to be associated with an electronic topological transition involving change in the Z 2 topological invariant. In addition to the electronic changes, our Raman experiments indicate that rhombohedral (R3m) SnBi 2 Te 4 undergoes structural transition at ∼6.0 to a possible monoclinic phase and another transition at ∼12.0 GPa. Raman and x-ray diffraction experiments on trigonal (P3m1) SnBi 4 Te 7 show two structural transitions at ∼9.5 GPa to a monoclinic phase followed by one to cubic phase at ∼14.1 GPa. Our analysis of electronic structure reveals that the phase transition at 9.5 GPa in SnBi 4 Te 7 is accompanied by an insulator to semimetal transition.
EPL (Europhysics Letters), 2014
Local and electronic structures of vanadium in VO2 are studied across the highpressure insulator-to-metal (IMT) transition using V K-edge x-ray absorption spectroscopy. Unlike the temperature-induced IMT, pressure-induced metallization leads to only subtle changes in the V K-edge prepeak structure, indicating a different mechanism involving smaller electronic spectral weight transfer close to the chemical potential. Intriguingly, upon application of the hydrostatic pressure, the electronic structure begins to show substantial changes well before the occurrence of the IMT and the associated structural transition to an anisotropic compression of the monoclinic metallic phase.
Nano letters, 2017
Van der Waals (vdW) forces, despite being relatively weak, hold the layers together in transition metal dichalcogenides (TMDs) and play a key role in their band structure evolution, hence profoundly affecting their physical properties. In this work, we experimentally probe the vdW interactions in MoS2 and other TMDs by measuring the valence band maximum (VBM) splitting (Δ) at K point as a function of pressure in a diamond anvil cell. As high pressure increases interlayer wavefunction coupling, the VBM splitting is enhanced in 2H-stacked MoS2 multilayers but, due to its specific geometry, not in 3R-stacked multilayers, hence allowing the interlayer contribution to be separated out of the total VBM splitting, as well as predicting a negative pressure (2.4 GPa) where the interlayer contribution vanishes. This negative pressure represents the threshold vdW interaction beyond which neighboring layers are electronically decoupled. This approach is compared to first-principles calculations...