CORRELATION BETWEEN STRUCTURAL STABILITY AND ELECTRONIC STRUCTURE OF UGa3 UP TO 30 GPa

2011 ◽  
Vol 25 (04) ◽  
pp. 551-559 ◽  
Author(s):  
V. KATHIRVEL ◽  
SHARAT CHANDRA ◽  
N. V. CHANDRA SHEKAR ◽  
P. CH. SAHU ◽  
M. RAJAGOPALAN
Keyword(s):  
Structural Stability ◽  
High Pressures ◽  
Structural Phase ◽  
Maximum Pressure ◽  
Full Potential ◽  
X Ray Diffraction ◽  
Pressure Derivative ◽  
Augmented Plane Wave ◽  
Diamond Anvil ◽  
Structure Calculations

High-pressure angle-dispersive X-ray diffraction experiments were performed on UGa 3 up to 30 GPa within a diamond-anvil cell. UGa 3 remains in its cubic AuCu 3 type structure up to the maximum pressure studied and does not show any structural phase transition. To understand the structural stability of UGa 3, band structure calculations were performed as a function of reduced volume using the full-potential linear augmented plane wave (FP-LAPW) method. The results show that the Fermi level coincides with a deep valley in the density of states (DOS) curve in the antiferromagnetic state, whereas it lies near a valley (towards the bonding side) in the nonmagnetic state. At high pressures, the DOS near EF does not show much variation in both the cases. The experimental and theoretical equation of state, bulk modulus, and its pressure derivative values are also reported. The pressure dependence of magnetic moment shows a linear decrease at the rate of dμ/dP = -0.027 μ B / GPa .

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.

Mechanical, spin polarized electronic and magnetic properties of TmX(X = Cu, Ag): First principle study

2015 ◽  
Vol 29 (03) ◽  
pp. 1550007 ◽  
Author(s):  
Satish Chand ◽  
R. P. Singh ◽  
A. Govindan ◽  
S. K. Singh
Keyword(s):  
Magnetic Behavior ◽  
Optimization Method ◽  
Lattice Parameter ◽  
Orbital Method ◽  
Full Potential ◽  
Pressure Derivative ◽  
Augmented Plane Wave ◽  
Spin Polarized ◽  
Derivative Formula ◽  
High Spin Polarization

To study the mechanical, spin polarized electronic and magnetic behavior of TmX (X = Cu, Ag) , full-potential linear augmented plane wave plus local orbital method has been used. The lattice parameter (a0), bulk modulus (B0) and its first-order pressure derivative [Formula: see text] have been calculated using optimization method. Mechanical properties have been studied in terms of elastic constants (Cij), Young's modulus (Y), shear modulus (G) and Poisson's ratio (v) at ambient temperature and pressure which are found to be consistent with available experimental/theoretical values. Electronic properties have been investigated in terms of band structure and density of state histograms for spin up and spin down channel. Electronic and magnetic behavior of TmX shows that studied materials are metallic ferromagnets with high spin polarization in which Tm-f state electrons are contributed mainly.

The Breathing Mode of BaBiO3: Electric Field Gradient and Total Energy Calculations

1994 ◽  
Vol 49 (1-2) ◽  
pp. 129-132 ◽  
Author(s):  
P. Blaha ◽  
K. Schwarz ◽  
P. Dufek ◽  
G. Vielsack ◽  
W. Weber
Keyword(s):  
Electric Field ◽  
Full Potential ◽  
Electric Field Gradients ◽  
Augmented Plane Wave ◽  
Breathing Mode ◽  
Field Gradients ◽  
Total Energies ◽  
Linearized Augmented Plane Wave ◽  
Structure Calculations ◽  
Oxygen Site

Abstract We present ab initio full-potential linearized augmented plane wave (LAPW) band structure calculations for BaBiO3. We focus on total energies and electric field gradients at the oxygen site and present results for the breathing mode in the experimentally observed cubic and monoclinic structures of doped and undoped Ba1-xKxBiO3.

First-Principles Calculations of the Structural, Electronic, Optical and Mechanical Properties of CdS, CdSe and CdTe

2013 ◽  
Vol 665 ◽  
pp. 302-306 ◽  
Author(s):  
Sheetal Sharma ◽  
Ajay Singh Verma
Keyword(s):  
Experimental Data ◽  
Density Functional ◽  
Full Potential ◽  
Generalized Gradient ◽  
Pressure Derivative ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
Zinc Blende ◽  
Optical And Mechanical Properties ◽  
Good Agreement

The structural, electronic, optical and elastic properties of zinc-blende compounds (CdX, X = S, Se and Te), were studied using full-potential augmented plane wave plus local orbitals method (FP-LAPW+ lo) within density functional theory, using generalized gradient approximation (GGA). Geometrical optimization of the unit cell (lattice constant, bulk modulus and its pressure derivative) is in good agreement with experimental data. Results for band structures, density of states, and elastic constants (C11, C12 and C44) are presented. We also report our results on optical properties like the complex dielectric functions and the refractive index (n) of these compounds. Our results are in reasonable agreement with the available theoretical and experimental data.

Structural, Electronic and Elastic Properties of CeTl Intermetallic Compound

2016 ◽  
Vol 28 ◽  
pp. 1-4
Author(s):  
Deepika Shrivastava ◽  
Sankar P. Sanyal
Keyword(s):  
Bulk Modulus ◽  
Elastic Properties ◽  
Density Functional ◽  
Full Potential ◽  
Generalized Gradient ◽  
Pressure Derivative ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
Cscl Type ◽  
Linearized Augmented Plane Wave

The structural, electronic and elastic properties of CeTl with CsCl-type B2 structure have been investigated using full-potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT) within the generalized gradient approximation (GGA) for exchange and correlation potential. The ground state properties such as lattice constant, bulk modulus and pressure derivative of bulk modulus have been calculated which are in good agreement with available experimental data. The band structure and density of state depict that 4f electrons of Ce element have dominant character in electronic conduction and are responsible for metallic character of CeTl. The charge density plot reveals that the metallic as well as ionic bonding exist between Ce and Tl atoms. The calculated elastic constants indicate that CeTl is mechanically stable in cubic B2 phase and found to be ductile in nature.

scholarly journals Theoretical Investigations of Structural Phase Transitions and Magnetic, Electronic and Thermal Properties of DyNi: Under High Pressures and Temperatures

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
Pooja Rana ◽  
U. P. Verma
Keyword(s):  
Thermal Properties ◽  
Rare Earth ◽  
Bulk Modulus ◽  
Density Functional ◽  
High Pressures ◽  
Magnetic Moments ◽  
Structural Phase ◽  
Rare Earth Ions ◽  
Full Potential ◽  
Electronic Band

Present work is influenced by the requirement of investigation of rare earth intermetallics due to the nonavailability of theoretical details and least information from experimental results. An attempt has been made to analyse the structural, electronic, magnetic and thermal properties of DyNi using full potential linear augmented plane wave method based on density functional theory. DyNi differs from other members of lanthanides nickelates as in ground state it crystallizes in FeB phase rather than orthorhombic CrB structure. The equilibrium lattice constant, bulk modulus, and pressure derivative of bulk modulus are presented in four polymorphs (FeB, CrB, CsCl and NaCl) of DyNi. At equilibrium the cell volume of DyNi for FeB structure has been calculated as 1098.16 Bohr3 which is comparable well with the experimental value 1074.75 Bohr3. The electronic band structure has been presented for FeB phase. The results for thermal properties, namely, thermal expansion coefficient, Gruneisen parameter, specific heat and Debye temperature at higher pressure and temperatures have been reported. The magnetic moments at equilibrium lattice constants have also been tabulated as the rare earth ions associated with large magnetic moments increase their utility in industrial field for the fabrication of electronic devices due to their magnetocaloric effect used in magnetic refrigeration.

scholarly journals Synthesis of clathrate cerium superhydride CeH9 at 80-100 GPa with atomic hydrogen sublattice

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Nilesh P. Salke ◽  
M. Mahdi Davari Esfahani ◽  
Youjun Zhang ◽  
Ivan A. Kruglov ◽  
Jianshi Zhou ◽  
...  
Keyword(s):  
Atomic Hydrogen ◽  
High Pressures ◽  
Structure Stability ◽  
X Ray Diffraction ◽  
Detailed Chemistry ◽  
X Ray ◽  
3 Dimensional ◽  
Diamond Anvil ◽  
Laser Heated ◽  
Very High

Abstract Hydrogen-rich superhydrides are believed to be very promising high-Tc superconductors. Recent experiments discovered superhydrides at very high pressures, e.g. FeH5 at 130 GPa and LaH10 at 170 GPa. With the motivation of discovering new hydrogen-rich high-Tc superconductors at lowest possible pressure, here we report the prediction and experimental synthesis of cerium superhydride CeH9 at 80–100 GPa in the laser-heated diamond anvil cell coupled with synchrotron X-ray diffraction. Ab initio calculations were carried out to evaluate the detailed chemistry of the Ce-H system and to understand the structure, stability and superconductivity of CeH9. CeH9 crystallizes in a P63/mmc clathrate structure with a very dense 3-dimensional atomic hydrogen sublattice at 100 GPa. These findings shed a significant light on the search for superhydrides in close similarity with atomic hydrogen within a feasible pressure range. Discovery of superhydride CeH9 provides a practical platform to further investigate and understand conventional superconductivity in hydrogen rich superhydrides.

scholarly journals Study on the High-Pressure Behavior of Goethite up to 32 GPa Using X-Ray Diffraction, Raman, and Electrical Impedance Spectroscopy

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 99 ◽  
Author(s):  
Ruilian Tang ◽  
Jiuhua Chen ◽  
Qiaoshi Zeng ◽  
Yan Li ◽  
Xue Liang ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Impedance Spectroscopy ◽  
Electrical Impedance ◽  
High Pressures ◽  
Structural Phase ◽  
Second Order ◽  
Electrical Impedance Spectroscopy ◽  
X Ray Diffraction ◽  
X Ray

Goethite is a major iron-bearing sedimentary mineral on Earth. In this study, we conducted in situ high-pressure x-ray diffraction, Raman, and electrical impedance spectroscopy measurements of goethite using a diamond anvil cell (DAC) at room temperature and high pressures up to 32 GPa. We observed feature changes in both the Raman spectra and electrical resistance at about 5 and 11 GPa. However, the x-ray diffraction patterns show no structural phase transition in the entire pressure range of the study. The derived pressure-volume (P-V) data show a smooth compression curve with no clear evidence of any second-order phase transition. Fitting the volumetric data to the second-order Birch–Murnaghan equation of state yields V0 = 138.9 ± 0.5 Å3 and K0 = 126 ± 5 GPa.

scholarly journals Experimental and Computational Studies on Superhard Material Rhenium Diboride under Ultrahigh Pressures

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1657 ◽  
Author(s):  
Kaleb C. Burrage ◽  
Chia-Min Lin ◽  
Wei-Chih Chen ◽  
Cheng-Chien Chen ◽  
Yogesh K. Vohra
Keyword(s):  
Density Functional ◽  
Hexagonal Phase ◽  
Extreme Environment ◽  
Ultrahigh Pressure ◽  
Maximum Pressure ◽  
Pressure Derivative ◽  
Crystal Anisotropy ◽  
Axis Compression ◽  
Diamond Anvil ◽  
Rhenium Diboride

An emerging class of superhard materials for extreme environment applications are compounds formed by heavy transition metals with light elements. In this work, ultrahigh pressure experiments on transition metal rhenium diboride (ReB2) were carried out in a diamond anvil cell under isothermal and non-hydrostatic compression. Two independent high-pressure experiments were carried out on ReB2 for the first time up to a pressure of 241 GPa (volume compression V/V0 = 0.731 ± 0.004), with platinum as an internal pressure standard in X-ray diffraction studies. The hexagonal phase of ReB2 was stable under highest pressure, and the anisotropy between the a-axis and c-axis compression increases with pressure to 241 GPa. The measured equation of state (EOS) above the yield stress of ReB2 is well represented by the bulk modulus K0 = 364 GPa and its first pressure derivative K0´ = 3.53. Corresponding density-functional-theory (DFT) simulations of the EOS and elastic constants agreed well with the experimental data. DFT results indicated that ReB2 becomes more ductile with enhanced tendency towards metallic bonding under compression. The DFT results also showed strong crystal anisotropy up to the maximum pressure under study. The pressure-enhanced electron density distribution along the Re and B bond direction renders the material highly incompressible along the c-axis. Our study helps to establish the fundamental basis for anisotropic compression of ReB2 under ultrahigh pressures.

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