scholarly journals Structural and electronic behaviour of MoS2, MoSe2and MoTe2at high pressure

2014 ◽  
Vol 70 (a1) ◽  
pp. C1619-C1619
Author(s):  
Liliana Grajcarova ◽  
Michaela Riflikova ◽  
Roman Martonak ◽  
Erio Tosatti
Keyword(s):  
High Pressure ◽  
Electronic Transition ◽  
Structural Changes ◽  
Structural Transition ◽  
Transition Metal Dichalcogenides ◽  
X Ray Diffraction ◽  
X Ray ◽  
Excitonic Insulator ◽  
Metal Dichalcogenides ◽  
Indirect Band Gap

Using ab initio calculations and metadynamics simulations we studied the behaviour of layered semiconducting transition metal dichalcogenides, MoX2 (X = S, Se, Te) at high pressure with focus on structural transitions and metallization [1,2]. We found that concerning structure, the behaviour of MoS2 is different from that of MoSe2 and MoTe2. In MoS2 pressure induces at 20 GPa a structural transition where layer sliding takes place, bringing the initial 2Hc stacking to a 2Ha stacking typical of e.g. 2H-NbSe2. This finding naturally explains previous X-ray diffraction and Raman spectroscopy data and was very recently confirmed by new X-ray diffraction experiments[3]. On the other hand, this transition does not occur in MoSe2 and MoTe2 where instead the initial 2Hc stacking remains stable. Besides structural changes pressure in MoS2 induces also a semiconductor - semimetal transition which takes place by band overlap and closing of indirect band gap. This electronic transition occurs in the same region where the structural transition takes place, at 25 GPa in the 2Hc phase and at 20 GPa in the 2Ha phase. In case of MoSe2 and MoTe2 a very similar electronic transition leading to semimetal is predicted to occur at 28 GPa and 13 GPa, respectively. All three materials exhibit after metallization a low density of states at the Fermi level implying low superconducting temperature (if any). Due to absence of structural transition in the metallization region MoSe2 and MoTe2 could be suitable candidate materials for observation of the excitonic insulator phase.

Lattice modulation in the hexagonal-type antiphase domain structure of Au–33at.%Cd alloy

1982 ◽  
Vol 15 (2) ◽  
pp. 174-181 ◽  
Author(s):  
Y. Watanbe ◽  
H. Iwasaki
Keyword(s):  
Crystal Structure ◽  
Transition Metal Dichalcogenides ◽  
Antiphase Domain ◽  
Charge Density Waves ◽  
Physical Significance ◽  
Intensity Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Metal Dichalcogenides ◽  
Antiphase Domains

The crystal structure of an ordered Au–33at.%Cd alloy has been reinvestigated by X-ray diffraction. Least-squares refinement using single-crystal intensity data collected by photographic methods has shown that mixed occupation by the two kinds of atoms preferentially occurs in the atomic sites located near the boundaries of the hexagonal antiphase domains, confirming the results obtained by electron diffraction [Hirabayashi, Yamaguchi, Hiraga, Ino, Sato & Toth (1970). d. Phys. Chem. Solids, 31, 77–94]. The refinement has also shown that many of the atoms are periodically displaced from the normal positions of the fundamental h.c.p. lattice. The physical significance of the occupancy and displacement modulations is discussed. The latter bears a resemblance to the motion of cations in the transition-metal dichalcogenides and the direction of the displacements in the alloy can be explained if charge-density waves synchronizing with the occupancy waves are assumed to exist.

scholarly journals The High Pressure Behavior of Galenobismutite, PbBi2S4: A Synchrotron Single Crystal X-ray Diffraction Study

Crystals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 210 ◽  
Author(s):  
Paola Comodi ◽  
Azzurra Zucchini ◽  
Tonci Balić-Žunić ◽  
Michael Hanfland ◽  
Ines Collings
Keyword(s):  
High Pressure ◽  
Single Crystal ◽  
Structural Changes ◽  
Calcium Ferrite ◽  
X Ray Diffraction ◽  
Third Order ◽  
Electron Pairs ◽  
X Ray ◽  
Cation Sites ◽  
Murnaghan Equation

High-pressure single-crystal synchrotron X-ray diffraction data for galenobismutite, PbBi2S4 collected up to 20.9 GPa, were fitted by a third-order Birch-Murnaghan equation of state, as suggested by a FE-fE plot, yielding V0 = 697.4(8) Å3, K0 = 51(1) GPa and K’ = 5.0(2). The axial moduli were M0a = 115(7) GPa and Ma’ = 28(2) for the a axis, M0b = 162(3) GPa and Mb’ = 8(3) for the b axis, M0c = 142(8) GPa and Mc’ = 26(2) for the c axis, with refined values of a0, b0, c0 equal to 11.791(7) Å, 14.540(6) Å 4.076(3) Å, respectively, and a ratio equal to M0a:M0b:M0c = 1.55:1:1.79. The main structural changes on compression were the M2 and M3 (occupied by Bi, Pb) movements toward the centers of their respective trigonal prism bodies and M3 changes towards CN8. The M1 site, occupied solely by Bi, regularizes the octahedral form with CN6. The eccentricities of all cation sites decreased with compression testifying for a decrease in stereochemical expression of lone electron pairs. Galenobismutite is isostructural with calcium ferrite CaFe2O4, the suggested high pressure structure can host Na and Al in the lower mantle. The study indicates that pressure enables the incorporation of other elements in this structure, increasing its potential significance for mantle mineralogy.

Investigation of the crystal structure of a low water content hydrous olivine to 29.9 GPa: A high-pressure single-crystal X-ray diffraction study

2020 ◽  
Vol 105 (12) ◽  
pp. 1857-1865
Author(s):  
Jingui Xu ◽  
Dawei Fan ◽  
Dongzhou Zhang ◽  
Bo Li ◽  
Wenge Zhou ◽  
...  
Keyword(s):  
High Pressure ◽  
Equation Of State ◽  
Single Crystal ◽  
Water Content ◽  
Structural Changes ◽  
Volume Data ◽  
Structural Refinement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Water Contents

Abstract Olivine is the most abundant mineral in the Earth's upper mantle and subducting slabs. Studying the structural evolution and equation of state of olivine at high-pressure is of fundamental importance in constraining the composition and structure of these regions. Hydrogen can be incorporated into olivine and significantly influence its physical and chemical properties. Previous infrared and Raman spectroscopic studies indicated that local structural changes occur in Mg-rich hydrous olivine (Fo ≥ 95; 4883–9000 ppmw water) at high-pressure. Since water contents of natural olivine are commonly <1000 ppmw, it is inevitable to investigate the effects of such water contents on the equation of state (EoS) and structure of olivine at high-pressure. Here we synthesized a low water content hydrous olivine (Fo95; 1538 ppmw water) at low SiO2 activity and identified that the incorporated hydrogens are predominantly associated with the Si sites. We performed high-pressure single-crystal X-ray diffraction experiments on this olivine to 29.9 GPa. A third-order Birch-Murnaghan equation of state (BM3 EoS) was fit to the pressure-volume data, yielding the following EoS parameters: VT0 = 290.182(1) Å3, KT0 = 130.8(9) GPa, and K′T0 = 4.16(8). The KT0 is consistent with those of anhydrous Mg-rich olivine, which indicates that such low water content has negligible effects on the bulk modulus of olivine. Furthermore, we carried out the structural refinement of this hydrous olivine as a function of pressure to 29.9 GPa. The results indicate that, similar to the anhydrous olivine, the compression of the M1-O and M2-O bonds are comparable, which are larger than that of the Si-O bonds. The compression of M1-O and M2-O bonds of this hydrous olivine are comparable with those of anhydrous olivine, while the Si-O1 and Si-O2 bonds in the hydrous olivine are more compressible than those in the anhydrous olivine. Therefore, this study suggests that low water content has negligible effects on the EoS of olivine, though the incorporation of water softens the Si-O1 and Si-O2 bond.

Structural stability of WS2 under high pressure

2014 ◽  
Vol 28 (25) ◽  
pp. 1450168 ◽  
Author(s):  
Nirup Bandaru ◽  
Ravhi S. Kumar ◽  
Jason Baker ◽  
Oliver Tschauner ◽  
Thomas Hartmann ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
High Temperature ◽  
Structural Changes ◽  
High Pressures ◽  
Structural Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diamond Anvil ◽  
Heating Up

Structural behavior of bulk WS 2 under high pressure was investigated using synchrotron X-ray diffraction and diamond anvil cell up to 52 GPa along with high temperature X-ray diffraction and high pressure Raman spectroscopy analysis. The high pressure results obtained from X-ray diffraction and Raman analysis did not show any pressure induced structural phase transformations up to 52 GPa. The high temperature results show that the WS 2 crystal structure is stable upon heating up to 600°C. Furthermore, the powder X-ray diffraction obtained on shock subjected WS 2 to high pressures up to 10 GPa also did not reveal any structural changes. Our results suggest that even though WS 2 is less compressible than the isostructural MoS 2, its crystal structure is stable under static and dynamic compressions up to the experimental limit.

scholarly journals Synthesis of Transition Metal Dichalcogenides based hybrid nanostructures by thermal decomposition method

2021 ◽  
Vol 2070 (1) ◽  
pp. 012095
Author(s):  
Melbin Baby ◽  
K. Rajeev Kumar
Keyword(s):  
Electron Microscopy ◽  
Thermal Decomposition ◽  
Decomposition Method ◽  
Transition Metal Dichalcogenides ◽  
Hybrid Nanostructures ◽  
Hybrid Nanostructure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Thermal Decomposition Method ◽  
Metal Dichalcogenides

Abstract In this work, we report synthesis of hybrid nanostructures of Transition Metal Dichalcogenides via thermal decomposition method. Ammonium tetrathiomolybdate was used as not only growth templates but also as starting precursor for synthesis of hybrid nanostructures. The conditions for the synthesizing method were optimized using electron microscopy and x-ray diffraction. In this hybrid nanostructure synthesis, it was found that MoO3 nanorods are interspersed on exfoliated MoS2 nanosheets. The structural and optical properties of the hybrid nanostructure were investigated using transmission electron microscopy (TEM), Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and Ultraviolet Visible spectrophotometry (UV-VIS). The hybrid nanostructure of MoO3 on MoS2 shows a band gap of 2.2 eV. It was also found that by tuning the preparation parameters viz temperature of heating and time of heating, the composition of the hybrid nanostructure can be varied.

scholarly journals Aberrant electronic and structural alterations in pressure tuned perovskite NaOsO3

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Raimundas Sereika ◽  
Peitao Liu ◽  
Bongjae Kim ◽  
Sooran Kim ◽  
Jianbo Zhang ◽  
...  
Keyword(s):  
High Pressure ◽  
Structural Transition ◽  
Metallic State ◽  
Polar Phase ◽  
X Ray Diffraction ◽  
Metal Insulator ◽  
X Ray ◽  
New States ◽  
Induced Changes ◽  
Electronic Character

Abstract The perovskite NaOsO3 has a metal–insulator transition at temperature 410 K, which is delicate, intriguing, and provokes a lot of debate on its nature. Our combined electrical resistance, Raman, and synchrotron x-ray diffraction experiments show that the insulating ground state in this osmate endures under high pressure up to at least 35 GPa. In this pressure range, compression reveals hidden hysteretic resistance properties with a transient metallic state near 200 K, manifested three electronic character anomalies (at 1.7, 9.0, and 25.5 GPa), and a structural transition to the singular polar phase (at ~18 GPa). We distinguish NaOsO3 from the regular crystallographic behavior of perovskites, though the electrical specificities resemble iridates and nickelates. The theoretical first-principle band structure and lattice dynamics calculations demonstrate that the magnetically itinerant Lifshitz-type mechanism with spin–orbit and spin–phonon interactions is responsible for these pressure-induced changes. Our findings provide another new playground for the emergence of new states in 5d materials by using high-pressure methods.

Structures of New Nitrides Prepared using Solid Oxide Precursors

1995 ◽  
Vol 410 ◽  
Author(s):  
Joel D. Houmes ◽  
David S. Bem ◽  
Hans-Conrad Zur Loye
Keyword(s):  
Solid State ◽  
Transition Metal ◽  
Transition Metal Dichalcogenides ◽  
Reaction Times ◽  
Solid Oxide ◽  
Metal Nitrides ◽  
Transition Metal Nitrides ◽  
X Ray Diffraction ◽  
X Ray ◽  
Metal Dichalcogenides

ABSTRACTSeveral novel transition metal nitrides and oxynitrides were synthesized via ammonolysis of solid state oxide precursors at temperatures ranging from 700°C-900°C and reaction times ranging from 12 hours to 4 days. The products were characterized by powder X-ray diffraction and their structures were determined by powder X-ray Rietveld refinement. The relationships between the structures of these nitrides and oxynitrides, and their similarity to the structures of the transition metal dichalcogenides, is discussed.

HIGH PRESSURE-HIGH TEMPERATURE ELECTRICAL RESISTIVITY STUDIES ON Nd0.9Ca0.1Ba2Cu3O7-δ

2006 ◽  
Vol 20 (29) ◽  
pp. 4885-4890
Author(s):  
R. SELVA VENNILA ◽  
S. REZA GHORBANI ◽  
N. VICTOR JAYA
Keyword(s):  
High Pressure ◽  
Electrical Resistivity ◽  
High Temperature ◽  
Bulk Modulus ◽  
Structural Changes ◽  
X Ray Diffraction ◽  
Heating Coil ◽  
X Ray ◽  
High Pressure High Temperature ◽  
Electrical Resistivity Study

High pressure-high temperature electrical resistivity study on composition-controlled Nd 0.9 Ca 0.1 Ba 2 Cu 3 O 7-δ high T c superconductor (HTSC) is carried out by a four-probe technique using Bridgman anvils. A simple heating coil arrangement is used for heating the samples. Electrical resistivity behavior under pressure (up to a maximum of 8 GPa) at various temperatures (up to a maximum of 523 K) were studied and reported in this paper. Simulation of energy dispersive X-ray diffraction confirms substitution of calcium at the Nd site of Nd -123. Variation of the electrical resistivity under pressure is compared with that of the structural changes and the bulk modulus was determined.

Behavior of carbon nanotubes under high pressure and high temperature

2000 ◽  
Vol 15 (2) ◽  
pp. 560-563 ◽  
Author(s):  
D. S. Tang ◽  
L. C. Chen ◽  
L. J. Wang ◽  
L. F. Sun ◽  
Z. Q. Liu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
High Pressure ◽  
High Temperature ◽  
Structural Changes ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Diamond Crystallization ◽  
Graphite Sheets

The structural changes of carbon nanotubes induced by high pressure and high temperature were investigated by means of x-ray diffraction, Raman scattering, scanning electron microscopy, and transmission electron microscopy. It is shown that, with increasing pressure and temperature, the lattice constant d002 of tubes shortens, and then tubes collapse into tapelike ones; at the same time the C–C bonds at high curvature break, which lead the tapelike tubes to break into graphite sheets as diamond crystallization centers. Compared with graphite, the diamond particles from carbon nanotubes have many defects as the trace of tubes.

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