Pressure Dependence Of Lattice Parameters Research Articles

Structural and elastic properties of TlInSe2 at high pressure

The results of the structural study of chain-like structured TlInSe2 compound using powder synchrotron X-ray diffraction (XRD) experiments under the pressures up to P = 30.53 GPa and a first principle analysis of structural and elastic properties under the pressures up to P = 50 GPa are reported. The XRD data show the stability of the tetragonal phase in the whole investigated pressure range. Density Functional Theory (DFT) calculations also evidence that at zero pressure the lowest energy structure of TlInSe2 is tetragonal (space symmetry group I4/mcm). At pressures above P ≥ 38 GPa the symmetry of the lowest energy structure changes to face-centered cubic one (Fm-3m). It was shown that the experimentally and theoretically obtained pressure dependences of lattice parameters in tetragonal phase are in good agreement. The pressure dependences of elastic constants, acoustic wave velocities and other elastic parameters, such as bulk modulus, shear modulus, Young's modulus, Poisson's ratio have been calculated.

High Pressure Effect on Structural and Electrochemical Properties of Anionic Redox-Based Lithium Transition Metal Oxides

Summary The richness of anionic redox chemistry in the solid state offers new opportunities and a possible paradigm shift in energy storage. The excess capacity that goes beyond conventional theoretical values is attributed to the anionic redox in Li-rich transition metal oxide cathodes for Li-ion batteries. Their electrochemical behavior is thermodynamically determined by structural evolution. To better understand the electrochemical dependence on structural factors, we have induced structural modifications in pristine and electrochemically activated Li1.144Ni0.136Co0.136Mn0.544O2 through high-pressure treatment. A unique cyclical change of structural reordering is observed in the anionic redox-activated material during operando pressure sweep, characterized by a periodic evolution of superlattice peak intensity in synchrotron X-ray diffraction patterns. During the structural reordering period, the bulk compressibility of the material decreases, even becoming negative. These insights elucidate the structural flexibility and metastability of anionic redox-based materials, which can undergo large compressions and structural modifications while delivering good electrochemical properties.

High-pressure angle-dispersive X-ray diffraction study of mechanically alloyed SnSe2

The effect of pressure on mechanically alloyed trigonal nanostructured SnSe2 (n-SnSe2) was studied by in situ angle-dispersive X-ray diffraction up to 25.8 GPa. The pressure dependence of lattice parameters and unit cell volume was investigated. By fitting the lattice parameters and unit cell volume to a third-order Birch–Murnaghan equation of state for several values of the applied pressure, the bulk modulus B0, its first derivative B′, and the linear moduli along the a- and c-axes were determined. The effect of pressure on the z coordinate of site 2d occupied by Se atoms was investigated using pair distribution function analysis. The results were compared with experimental and theoretical studies of SnS2 and SnSe2 reported in the literature.

High pressure study of structural, electronic, elastic, and vibrational properties of NaNb3O8

In this work, the structural, electronic, elastic and vibrational properties of orthorhombic Pmnm NaNb3O8 are investigated by means of ab initio total energy calculations. The obtained structural parameters are in good agreement with experimental data available at zero pressure. Furthermore, we study the pressure dependence of lattice parameters, bond lengths and bulk moduli of the constituent polyhedra. The electronic band structure is discussed from the density of states and the gap evolution under pressure is analyzed. The change of the elastic constants and the major elastic moduli, with the pressure are described, and several anisotropy indices are evaluated. Frequency, symmetry, pressure coefficients and Grüneisen parameters of phonon modes are reported. We discuss also the mechanical and dynamical stability and we conclude that the compound is dynamically unstable above 5.7 GPa.

Equation of state and lattice parameter of SnO2 nanomaterial

We developed a simple theoretical model to study the effect of pressure, temperature, shape and size on nanomaterials. We used the model to study the Equation of state (EOS) and pressure dependence of lattice parameter of SnO2­ nanomaterial. We selected SnO2 as an example because of the fact that the required experimental data are available so that a comparison of the results may be presented. We used the model to study the compression behaviour at room temperature and compared our results with the experimental data as well as with those based on Birch- Murnaghan Equation of state (BMEOS). Our results are found to present a good agreement with the experimental data as well as with those based on BMEOS. Due to the simplicity and applicability of the model, we extended our studies at different temperatures i.e. 300 K, 500 K and 700 K. A shift in the isotherms has been obtained. We also included the effect of shape and size in the EOS model to make it widely applicable for nanosystems. The results of pressure dependence of lattice parameter for SnO2 are compared with available experimental data. A good agreement between theory and experiment supports the validity of the model developed.

High Pressure Structural Investigation of Benzoic Acid: Raman Spectroscopy and X-ray Diffraction

The structural stability of benzoic acid (C6H5COOH, BA), a hydrogen-bonded molecular crystal, has been investigated by Raman spectroscopy and angle-dispersive X-ray diffraction (ADXRD) up to ∼18 GPa at room temperature. Under ambient conditions, benzoic acid molecules are arranged in two sets of parallel planes and held together by hydrogen bonding and van der Waals interactions. Small changes (e.g., emergence of new peaks, splitting of original peaks) can be observed in the Raman spectra at high pressures. However, no obvious changes can be observed in the X-ray diffraction measurements, which rules out any symmetry/structure changes within this pressure range. The pressure dependence of lattice parameters is presented, which shows monotonously decrease without any anomalies. The experimental isothermal pressure–volume data are well fitted by the third-order Birch–Murnaghan equation of state, yielding bulk modulus B0 = 41.7(6) GPa and a first pressure derivative B0′ = 4.5(4). Axial compressibility shows ...

First principle calculations of solid nitrobenzene under high pressure

The dispersion corrected density functional theory (DFT-D) calculations were performed to study the structural and vibrational properties of solid nitrobenzene at ambient pressure. Assignments of the calculated vibrational modes were provided. Moreover, using the norm-conserving pseudopotential plus GGA-PBE function, the unit cell parameters, geometries and vibrational frequencies of nitrobenzene were examined under hydrostatic pressure from 0 to 10GPa. The calculated pressure dependence of lattice parameters and volume were found to be close to the experimental results, but a distinct change in the bond lengths and bond angles was found around 7GPa. According to the phonon calculations, the pressure-induced changes of the vibrational frequencies were also observed around 7GPa. These calculated results all suggest a possible structural transformation in the crystalline nitrobenzene.

Absence of Metallic Conductivity in Tetragonal and Cubic PbVO3 at High Pressure

Transport properties of PbVO3, a material whose structural and electronic properties bear similarities with high-temperature copper superconductors, were investigated between 2 and 300 K and in the pressure range of 0.1 MPa and 11.3 GPa. There is a structural phase transition from about 2 GPa at room temperature from a super-tetragonal phase to a cubic phase with a significant drop of resistivity by about 5 orders of magnitude. Nevertheless, the cubic phase exhibited a semiconducting behavior of resistivity between 2 and 300 K up to 11.3 GPa. The pressure dependence of lattice parameters of the tetragonal and cubic phases was in very good agreement with results of first-principle calculations from J. Phys.: Condens. Matter 24, 435403 (2012). Fitting with the Birch–Murnaghan equation of states gave a bulk modulus K0 = 38.0(1.1) GPa and a unit cell volume V0 = 67.63(6) A3 for the tetragonal phase and K0 = 179.5(1.4) GPa and V0 = 58.272(14) A3 for the cubic phase.

Elastic and electronic properties of cubic cerium oxide under pressure via first principles

The elastic and electronic properties of cubic structure CeO 2 under pressure are investigated in the frame of density functional theory (DFT). By using the local-density approximation (LDA) plus U( LDA +U) method with U = 6 eV, the calculated lattice parameters, bulk modulus and elastic properties of the cubic CeO 2 at 0 GPa and 0 K are in good agreement with the available experimental data. The pressure dependences of lattice parameters, bulk and shear modulus, Debye temperature, Young's moduli, Poisson's ratio and the compressional and shear wave velocities of the cubic CeO 2 are obtained successfully. In addition, the total density of states (TDOS) and the band gaps of the cubic CeO 2 under pressures are also investigated. By comparing the results of LDA and LDA+U, both the conventional LDA and the LDA+U methods can be used to describe the structure of the cubic CeO 2 due to the electronic localization of 4f-electron in Ce which is not so strong. However, the LDA+U approach can obtain a proper shape of the density of electronic states that agrees well with the measured values.

First principles calculations of solid phase transition of nitromethane

The solid phase transition in crystals prepared from molecular energetic materials under extreme conditions is important for understanding the detonation mechanisms. By applying the first principles density functional calculations, a detailed theoretical study of the lattice parameters and molecular structures, equations of state, densities of state for solid nitromethane is reported. By analyzing the pressure dependence of lattice parameters, a sudden change of the lattice parameters occurs between 10-12 GPa, implying that a transition has taken place. It is also found that the maximum dihedral angle of H-C-N-O has increased from 155.3° to 177.5°, indicating that a rotation of the methyl group from a staggered to an eclipsed conformation occurs in the pressure range 11–12 GPa. Before the phase transition, the intramolecular O … H–C interactions are mainly of hydrogen bonds. After the phase transition, the intramolecular and intermolecular O … H interactions are mainly of the hydrogen bonds. Phase transition also affects the reduced ratio of band gap and the density of state near the Fermi level.

Pressure-induced group-subgroup phase transitions and post-cotunnite phases in actinide dioxides

Taking uranium dioxide and plutonium dioxide as prototypes, the phase stabilities of actinide dioxides under high pressures are studied with density functional theory. The calculations are carried out within the framework of Perdew-Burke-Ernzerhof (PBE) and PBE$+U$ formalism. Beyond the cotunnite Pnma phase, two novel orthorhombic phases with space groups $Cmc{2}_{1}$ and Cmcm are found as the possible ground state. Both of them are low temperature distortions of the hexagonal Ni${}_{2}$In phase with space group $P{6}_{3}/mmc$, which is a common post-cotunnite phase adopted by many AX${}_{2}$ and A${}_{2}$X binary compounds. According to the PBE$+U$ calculations, the $Cmc{2}_{1}$ phase is stable above $120\phantom{\rule{0.28em}{0ex}}\text{GPa}$ in UO${}_{2}$, and it transforms to the Cmcm phase at around $400\phantom{\rule{0.28em}{0ex}}\text{GPa}$. In PuO${}_{2}$, the Pnma phase directly transforms to the Cmcm phase at $123\phantom{\rule{0.28em}{0ex}}\text{GPa}$. Symmetry analysis shows that the transitions of $Cmc{2}_{1}$ to Cmcm in UO${}_{2}$ and Pnma to Cmcm in PuO${}_{2}$ are pressure induced group-subgroup transitions. The Cmcm phase is responsible for pressure-induced metallization both in UO${}_{2}$ and PuO${}_{2}$, but their electronic structures are quite different during metallization. The difference is originated from their insulating nature, where UO${}_{2}$ is a standard Mott-Hubbard insulator, while PuO${}_{2}$ belongs to an intermediate region between the Mott-Hubbard insulator and charge-transfer insulator. The equations of state are also analyzed, together with the pressure dependence of lattice parameters, fractional atomic coordinates, electronic band gap, and magnetic moment. The results indicate that these distorted-Ni${}_{2}$In phases will probably be adopted by other actinide dioxides.

Structural phase transition in Bi2Te3 under high pressure†

Structural change in Bi2Te3 under high pressure up to 16.6 GPa has been studied by powder x-ray diffraction. We observed two times of phase transitions at room temperature at the pressures of 8 and 14 GPa, respectively. According to our preliminary result on electrical resistance, it is reasonable to suppose that superconducting transition with T c =2.8 K at the pressures of 10.2 GPa is observed in phase II. On the other hand, we found anomalies of the pressure dependences of lattice parameters and volume at around 2 GPa, which probably means the change in electrical structure on the Fermi surface. †This paper was presented at the XLVIth European High Pressure Research Group (EHPRG 46) Meeting, Valencia (Spain), 7–12 September, 2008.

Structure and elastic properties of boron suboxide at 240 GPa

Structure and elastic properties of boron suboxide at high pressure have been investigated using generalized gradient approximation within the plane-wave pseudopotential density functional theory. The elastic constants are calculated using the finite strain method. The pressure dependences of lattice parameters, elastic constants, aggregate elastic moduli, and sound velocities of boron suboxide are predicted. It is found that the most stable structure of hcp boron suboxide at zero pressure corresponds to the ratio c/a of about 2.274 and the equilibrium lattice parameters a0 and c0 are about 5.331 and 12.124 Å, respectively. The high-pressure elastic constants indicate that boron suboxide is mechanically stable up to 368 GPa. The pressure dependence of the calculated normalized volume and the aggregate elastic moduli agree well with the recent experimental results. The sound velocities along different directions for the structure of boron suboxide are obtained. It shows that the velocities of the shear wave decrease as pressure increases but those of all the longitudinal waves increase with pressure. Moreover, the azimuthal anisotropy of the compression and shear aggregate wave velocities for different pressures are predicted. They change behavior with increasing pressure around 87 GPa because of an electronic topological transition. A refined analysis has been made to reveal the high pressure elastic anisotropy in boron suboxide.

Influence of high hydrostatic pressure on lattice parameters of a single crystal of La3Nb0.5Ga5.5O14

Abstract Unit-cell parameters of La3Nb0.5Ga5.5O14 (langanite) have been determined at a number of pressures up to 23GPa in diamond anvil high pressure cells with single crystal X-ray diffraction techniques. The anisotropic behaviour of unit cell parameters of langanite is caused by differences of bonding strength in direction parallel to the a- and c-axis. Within the investigated pressure range, the c/a-ratio increases from 0.6232 to 0.6503. The volume compressibility of trigonal langanite (space group P321) is the 0.007 GPa-1, with calculated bulk modulus of 145(3)GPa (B'0=1.4(8)). At a pressure of 12.4(3)GPa a first-order phase transition was detected, characterised by a discontinuity in the pressure dependence of lattice parameter c. The high-pressure phase (presumably monoclinic, A2) with a volume compressibility of 0.011 GPa-1 (B0=93(2) GPa, B'0=1.9(9)) is more compressible as compared to the initial phase due to an abnormal pressure dependence of lattice parameter a.

Collapse of the charge disproportionation and covalency-driven insulator-metal transition inSr3Fe2O7under pressure

The effect of pressure on electronic properties and crystal structure of ${\mathrm{Sr}}_{3}{\mathrm{Fe}}_{2}{\mathrm{O}}_{7}$ was studied up to 45 GPa. Experimental methods employed were ${}^{57}\mathrm{Fe}$ M\"ossbauer spectroscopy (MS), monochromatic synchrotron powder x-ray diffraction, optical reflectance between 0.6 and 4 eV, and electrical resistance measurements. M\"ossbauer spectra of the magnetically ordered as well as of the paramagnetic phase demonstrate that the charge disproportionation of ${\mathrm{Fe}}^{\mathrm{IV}}$ disappears at pressures between 15 and 21 GPa. The diffraction data show that the tetragonal Ruddlesden-Popper-type crystal structure (space group $I4/mmm)$ is retained up to the highest pressure. The optical spectra reveal a continuous increase with pressure of the near-infrared oscillator strength, which indicates a pressure-driven transition from an insulating towards a metallic ground state. This is confirmed by the electrical resistance measurements which evidence a sluggish pressure-induced insulator-metal (IM) transition with a clear incipient metallic state at $P\ensuremath{\approx}20$ GPa. The changes in electronic state are not associated with any detectable anomaly in the pressure dependence of lattice parameters. The high-pressure behavior of ${\mathrm{Sr}}_{3}{\mathrm{Fe}}_{2}{\mathrm{O}}_{7}$ is discussed in terms of a strengthening of the covalent $\mathrm{Fe}(3d)\ensuremath{-}\mathrm{O}(2p)\ensuremath{-}\mathrm{Fe}(3d)$ interactions under pressure. Within the impurity model for the electronic structure of transition metal compounds the IM transition in ${\mathrm{Sr}}_{3}{\mathrm{Fe}}_{2}{\mathrm{O}}_{7}$ can be attributed to the closure of a $p\ensuremath{-}p$-type energy gap. The ambient- and high-pressure properties of ${\mathrm{Sr}}_{3}{\mathrm{Fe}}_{2}{\mathrm{O}}_{7}$ and related ${\mathrm{Fe}}^{\mathrm{IV}}$ oxides are compared.

Effect of Pressure on the Superconducting Properties of YNi2B2C.

Electrical resistance of YNi2B2C has been measured at high pressure and magnetic field. The pressure dependence of lattice parameters was also measured up to 12 GPa at room temperature. It is found that the upper critical field Hc2 decreases slightly by applying pressure and a small anisotropy is observed in the lattice compression. The compressibilities along a- and c-axis are obtained to be Ka=1. 8×10-3 GPa-1 and Kc=2. 2×10-3 GPa-1, respectively. The present results are compared with those of other borocarbides.

Crystal chemistry of forsterite; a first-principles study

Other| August 01, 1997 Crystal chemistry of forsterite; a first-principles study Renata M. Wentzcovitch; Renata M. Wentzcovitch University of Minnesota, Department of Chemical Engineering and Materials Sciences, Minneapolis, MN, United States Search for other works by this author on: GSW Google Scholar Lars Stixrude Lars Stixrude Georgia Institute of Technology, United States Search for other works by this author on: GSW Google Scholar American Mineralogist (1997) 82 (7-8): 663–671. https://doi.org/10.2138/am-1997-7-802 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Renata M. Wentzcovitch, Lars Stixrude; Crystal chemistry of forsterite; a first-principles study. American Mineralogist 1997;; 82 (7-8): 663–671. doi: https://doi.org/10.2138/am-1997-7-802 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract We present a first-principles study (local density approximation) of the structural properties of forsterite under pressure. This highly anisotropic magnesium orthosilicate is the most abundant phase of the Earth’s upper mantle, and its elastic properties determine the rheology of this region. We perform full structural optimizations and investigate its compressive behavior up to 25 GPa. We obtain a pressure dependence of lattice parameters that agrees well with experiments to 17.2 GPa. We predict that the coordination polyhedra compress essentially isotropically, and we explain the anisotropy of forsterite in terms of the nonuniform distribution of coordination polyhedra having different but nearly uniform compressibilities. In agreement with Brodholt et al. (1996), we do not find theoretical evidence for sudden changes in compression mechanisms in this mineral as had been suggested from experiments. Our results support the hypothesis that such compressive anomalies are caused by solidification of the pressure medium. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Pressure Dependence of Magnetic Transition Temperatures and Lattice Parameter in an Antiferromagnetic Ordered Alloy Mn3Pt

The ordered alloy Mn 3 Pt is an antiferromagnet (AF) which shows an AF(D)-AF(F) transition at T C =365 K below the Neel temperature of the F phase T N (F) of 475 K. The pressure dependence of magnetic transition temperatures was studied up to 9.8 kbar. By application of pressure, T N (F) decreases with d T N (F)/d P =-7 K/kbar and T C increases with d T C /d P =14 K/kbar. Above 3.2 kbar, the antiferromagnetic F phase disappears, only the D phase appears and its Neel temperature T N (D) increases with d T N (D)/d P =5 K/kbar with further increase in pressure. The pressure dependence of lattice parameter was measured up to 52 kbar. The volume compressibility was obtained to be 0.9×10 -3 kbar -1 . The magnetic transition temperature vs pressure and lattic parameter phase diagrams were determined.

Effect of hydrostatic pressure on the phase transition of ferroelectric PbTiO 3

The effect of hydrostatic pressure on the dielectric constant of the Nb-doped lead titanate ceramics was measured up to 60 kbar at room temperature. From the previously observed pressure dependence of lattice parameters and the present results, it is concluded that the tetragonality decreases linearly with a slope of −7.6×10 −4/kbar and that the pressure dependence of the tetragonal-cubic transition temperature is −8.4K/kbar.