Surface Properties, Crystal Morphology, and Reactivity of La2Zr2O7-based Cathode Infiltrate in Solid Oxide Fuel Cells: A Theoretical Study

2011 ◽  
Vol 1327 ◽  
Author(s):  
Yves A. Mantz
Keyword(s):  
Density Functional ◽  
Strong Dependence ◽  
Perfect Crystal ◽  
Free Energies ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
Lanthanum Zirconate ◽  
Xrd Patterns ◽  
Stable Surfaces ◽  
Pyrochlore Oxide

ABSTRACTSelected properties of the lanthanum zirconate (La2Zr2O7, LZ) low-index faces, representing the first theoretical attempt to characterize the surfaces of a pyrochlore oxide, as well as oxygen (O2) interacting with LZ are predicted at the level of density-functional theory. All possible surface terminations formed by cleaving a perfect crystal are considered, as well as selected defective surfaces. After deriving the expression for the free energy of an LZ surface, surface free energies are computed. The most stable surfaces are identified, and it is suggested how to refine the ratios of surface free energies for comparison to experimental results obtained by the analysis of x-ray diffraction (XRD) patterns. The interaction of O2 with selected faces is examined. A strong dependence of the binding energy on surface oxygen content is predicted.

Defect-free and Defective Surfaces of the Pyrochlore Oxide La2Zr2O7: A Theoretical Study

2011 ◽  
Vol 1370 ◽  
Author(s):  
Yves A. Mantz
Keyword(s):  
Density Functional Theory ◽  
Free Energy ◽  
Electronic Structures ◽  
Density Functional ◽  
Theoretical Study ◽  
Perfect Crystal ◽  
Free Energies ◽  
Functional Theory ◽  
Lanthanum Zirconate ◽  
Pyrochlore Oxide

ABSTRACTIn this work, the low index faces of lanthanum zirconate (La2Zr2O7, LZ) are studied at the level of density-functional theory, representing the first theoretical attempt to characterize the surfaces of a pyrochlore oxide. All possible surface terminations formed by cleaving a perfect crystal are considered, as well as selected defective surfaces. After deriving the expression for the free energy of an LZ surface, surface free energies are computed. The most stable surface terminations are identified, their geometric and electronic structures discussed, and a motivation provided for calculating ratios of certain surface free energies more accurately for comparison to experimental results that will be obtained.

scholarly journals Classical Polarizable Force Field to Study Hydrated Hectorite: Optimization on DFT Calculations and Validation against XRD Data

Minerals ◽  
2018 ◽  
Vol 8 (5) ◽  
pp. 205 ◽  
Author(s):  
Ragnhild Hånde ◽  
Vivien Ramothe ◽  
Stéphane Tesson ◽  
Baptiste Dazas ◽  
Eric Ferrage ◽  
...  
Keyword(s):  
Force Field ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
X Ray Diffraction ◽  
Electronic Density ◽  
Functional Theory ◽  
Polarizable Force Field ◽  
Xrd Patterns ◽  
The One ◽  
Dynamics Simulations

Following our previous works on dioctahedral clays, we extend the classical Polarizable Ion Model (PIM) to trioctahedral clays, by considering dry Na-, Cs-, Ca- and Sr-hectorites as well as hydrated Na-hectorite. The parameters of the force field are determined by optimizing the atomic forces and dipoles on density functional theory calculations. The simulation results are validated by comparison with experimental X-ray diffraction (XRD) data. The XRD patterns calculated from classical molecular dynamics simulations performed with the PIM force field are in very good agreement with experimental results. In the bihydrated state, the less structured electronic density profile obtained with PIM compared to the one from the state-of-the-art non-polarizable force field clayFF explains the slightly better agreement between the PIM results and experiments.

scholarly journals Theoretical Investigations of a BN Polymorph with sp2 + sp3 Hybridizations

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1574
Author(s):  
Xinhai Yu ◽  
Riguge Su ◽  
Bei He ◽  
Binchang Ma
Keyword(s):  
Density Functional ◽  
Mechanical Anisotropy ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Theoretical Investigations ◽  
M Phase ◽  
The Difference ◽  
The Stability ◽  
Xrd Patterns

The crystal structure, mechanical anisotropy, elastic properties and electronic characteristics, as well as the stability, of P4/m BN are predicted by means of density functional theory. In this work, BN in the P4/m phase demonstrates mechanical and dynamical stability. Compared with the values of bulk B, E and G in the P4/m phase, the B of BN in the P4/m phase is greater than that of dz4 BN, while the G and E of P4/m BN are greater than those of Pnc2 BN and dz4 BN. The ratio of the bulk-to-shear modulus for P4/m BN is less than 1.75 and dz4 BN, dz2 BN and lzlz2 BN, indicating that P4/m BN is more brittle than dz4 BN, dz2 BN and lzlz2 BN. P4/m BN exhibits stronger mechanical anisotropy in G and E than Pbca BN, P42/mnm BN and Pm-3m BN but much weaker mechanical anisotropy than P4/mbm BN, B7N7, B11N11 and B15N15. In addition, P4/m BN is a quasi-direct bandgap semiconductor, and the difference between the direct and the indirect bandgap is 0.008 eV. In order to obtain further characteristics of P4/m BN for future synthetic verification, the X-ray diffraction (XRD) patterns for P4/m BN are also calculated. Given its properties, P4/m BN is a good candidate for photoelectric devices.

X-ray diffraction and density functional theory studies of R(Fe0.5Co0.5)O3 (R = Pr, Nd, Sm, Eu, Gd)

2016 ◽  
Vol 31 (4) ◽  
pp. 259-266 ◽  
Author(s):  
W. Wong-Ng ◽  
G. Liu ◽  
I. Levin ◽  
I. Williamson ◽  
P. Ackerman ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Transmission Electron ◽  
Bond Strain ◽  
Xrd Patterns

The structure of a series of lanthanide iron cobalt perovskite oxides, R(Fe0.5Co0.5)O3 (R = Pr, Nd, Sm, Eu, and Gd), have been investigated. The space group of these compounds was confirmed to be orthorhombic Pnma (No. 62), Z = 4. From Pr to Gd, the lattice parameter a varies from 5.466 35(13) Å to 5.507 10(13) Å, b from 7.7018(2) to 7.561 75(13) Å, c from 5.443 38(10) to 5.292 00(8) Å, and unit-cell volume V from 229.170(9) Å3 to 220.376(9) Å3, respectively. While the trend of V follows the trend of the lanthanide contraction, the lattice parameter “a” increases as the ionic radius r(R3+) decreases. X-ray diffraction (XRD) and transmission electron microscopy confirm that Fe and Co are disordered over the octahedral sites. The structure distortion of these compounds is evidenced in the tilt angles θ, ϕ, and ω, which represent rotations of an octahedron about the pseudocubic perovskite [110]p, [001]p, and [111]p axes. All three tilt angles increase across the lanthanide series (for R = Pr to R = Gd: θ increases from 12.3° to 15.2°, ϕ from 7.5° to 15.8°, and ω from 14.4° to 21.7°), indicating a greater octahedral distortion as r(R3+) decreases. The bond valence sum for the sixfold (Fe/Co) site and the eightfold R site of R(Fe0.5Co0.5)O3 reveal no significant bond strain. Density Functional Theory calculations for Pr(Fe0.5Co0.5)O3 support the disorder of Fe and Co and suggest that this compound to be a narrow band gap semiconductor. XRD patterns of the R(Fe0.5Co0.5)O3 samples were submitted to the Powder Diffraction File.

scholarly journals Exo⇔Endo Isomerism, MEP/DFT, XRD/HSA-Interactions of 2,5-Dimethoxybenzaldehyde: Thermal, 1BNA-Docking, Optical, and TD-DFT Studies

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5970
Author(s):  
Nabil Al-Zaqri ◽  
Mohammed Suleiman ◽  
Anas Al-Ali ◽  
Khaled Alkanad ◽  
Karthik Kumara ◽  
...  
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Structural Parameters ◽  
Population Analysis ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
Optical Energy Gap ◽  
Functional Theory ◽  
Reactivity Descriptors ◽  
Td Dft

The exo⇔endo isomerization of 2,5-dimethoxybenzaldehyde was theoretically studied by density functional theory (DFT) to examine its favored conformers via sp2–sp2 single rotation. Both isomers were docked against 1BNA DNA to elucidate their binding ability, and the DFT-computed structural parameters results were matched with the X-ray diffraction (XRD) crystallographic parameters. XRD analysis showed that the exo-isomer was structurally favored and was also considered as the kinetically preferred isomer, while several hydrogen-bonding interactions detected in the crystal lattice by XRD were in good agreement with the Hirshfeld surface analysis calculations. The molecular electrostatic potential, Mulliken and natural population analysis charges, frontier molecular orbitals (HOMO/LUMO), and global reactivity descriptors quantum parameters were also determined at the B3LYP/6-311G(d,p) level of theory. The computed electronic calculations, i.e., TD-SCF/DFT, B3LYP-IR, NMR-DB, and GIAO-NMR, were compared to the experimental UV–Vis., optical energy gap, FTIR, and 1H-NMR, respectively. The thermal behavior of 2,5-dimethoxybenzaldehyde was also evaluated in an open atmosphere by a thermogravimetric–derivative thermogravimetric analysis, indicating its stability up to 95 °C.

Site preference and atomic ordering in the ternary Rh5Ga2As: first-principles calculations

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Nilanjan Roy ◽  
Sucharita Giri ◽  
Harshit ◽  
Partha P. Jana
Keyword(s):  
Total Energy ◽  
First Principles ◽  
Density Functional ◽  
Structure Type ◽  
Site Preference ◽  
X Ray Diffraction ◽  
Atomic Ordering ◽  
Functional Theory ◽  
The Stability ◽  
Bonding Characteristics

Abstract The site preference and atomic ordering of the ternary Rh5Ga2As have been investigated using first-principles density functional theory (DFT). An interesting atomic ordering of two neighboring elements Ga and As reported in the structure of Rh5Ga2As by X-ray diffraction data only is confirmed by first-principles total-energy calculations. The previously reported experimental model with Ga/As ordering is indeed the most stable in the structure of Rh5Ga2As. The calculation detected that there is an obvious trend concerning the influence of the heteroatomic Rh–Ga/As contacts on the calculated total energy. Interestingly, the orderly distribution of As and Ga that is found in the binary GaAs (Zinc-blende structure type), retained to ternary Rh5Ga2As. The density of states (DOS) and Crystal Orbital Hamiltonian Population (COHP) are calculated to enlighten the stability and bonding characteristics in the structure of Rh5Ga2As. The bonding analysis also confirms that Rh–Ga/As short contacts are the major driving force towards the overall stability of the compound.

scholarly journals Measuring the structure and equation of state of polyethylene terephthalate at megabar pressures

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
J. Lütgert ◽  
J. Vorberger ◽  
N. J. Hartley ◽  
K. Voigt ◽  
M. Rödel ◽  
...  
Keyword(s):  
Equation Of State ◽  
Polyethylene Terephthalate ◽  
Density Functional ◽  
Equations Of State ◽  
Md Simulations ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
Shock Hugoniot ◽  
Highly Correlated

AbstractWe present structure and equation of state (EOS) measurements of biaxially orientated polyethylene terephthalate (PET, $$({\hbox {C}}_{10} {\hbox {H}}_8 {\hbox {O}}_4)_n$$ ( C 10 H 8 O 4 ) n , also called mylar) shock-compressed to ($$155 \pm 20$$ 155 ± 20 ) GPa and ($$6000 \pm 1000$$ 6000 ± 1000 ) K using in situ X-ray diffraction, Doppler velocimetry, and optical pyrometry. Comparing to density functional theory molecular dynamics (DFT-MD) simulations, we find a highly correlated liquid at conditions differing from predictions by some equations of state tables, which underlines the influence of complex chemical interactions in this regime. EOS calculations from ab initio DFT-MD simulations and shock Hugoniot measurements of density, pressure and temperature confirm the discrepancy to these tables and present an experimentally benchmarked correction to the description of PET as an exemplary material to represent the mixture of light elements at planetary interior conditions.

A DFT study of spherands containing five anisyl groups — Highly preorganized to bind the alkali metal

2006 ◽  
Vol 84 (8) ◽  
pp. 1045-1049 ◽  
Author(s):  
Shabaan AK Elroby ◽  
Kyu Hwan Lee ◽  
Seung Joo Cho ◽  
Alan Hinchliffe
Keyword(s):  
Density Functional Theory ◽  
Binding Energy ◽  
Density Functional ◽  
Ionic Radius ◽  
Binding Energies ◽  
Cavity Size ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Good Agreement

Although anisyl units are basically poor ligands for metal ions, the rigid placements of their oxygens during synthesis rather than during complexation are undoubtedly responsible for the enhanced binding and selectivity of the spherand. We used standard B3LYP/6-31G** (5d) density functional theory (DFT) to investigate the complexation between spherands containing five anisyl groups, with CH2–O–CH2 (2) and CH2–S–CH2 (3) units in an 18-membered macrocyclic ring, and the cationic guests (Li+, Na+, and K+). Our geometric structure results for spherands 1, 2, and 3 are in good agreement with the previously reported X-ray diffraction data. The absolute values of the binding energy of all the spherands are inversely proportional to the ionic radius of the guests. The results, taken as a whole, show that replacement of one anisyl group by CH2–O–CH2 (2) and CH2–S–CH2 (3) makes the cavity bigger and less preorganized. In addition, both the binding and specificity decrease for small ions. The spherands 2 and 3 appear beautifully preorganized to bind all guests, so it is not surprising that their binding energies are close to the parent spherand 1. Interestingly, there is a clear linear relation between the radius of the cavity and the binding energy (R2 = 0.999).Key words: spherands, preorganization, density functional theory, binding energy, cavity size.

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