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.

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.

Reactivity of the free and (5,5)-carbon nanotube-supported AuPt bimetallic clusters towards O2 activation: a theoretical study

2015 ◽  
Vol 17 (5) ◽  
pp. 3659-3672 ◽  
Author(s):  
Fazel Shojaei ◽  
Masoumeh Mousavi ◽  
Fariba Nazari ◽  
Francesc Illas
Keyword(s):  
Density Functional Theory ◽  
Carbon Nanotube ◽  
Electronic Structures ◽  
Density Functional ◽  
Theoretical Study ◽  
Bimetallic Clusters ◽  
Functional Theory ◽  
O2 Activation

Density functional theory (DFT)-based calculations were carried out to predict the geometry, energy and electronic structures of the small bimetallic AumPtn (2 ≤ m + n ≤ 4) clusters deposited on a single-wall (5,5)-carbon nanotube (CNT).

Density functional theory study of transition metal single-atoms anchored on graphyne as efficient electrocatalysts for the nitrogen reduction reaction

2021 ◽  
Author(s):  
Wei Song ◽  
Kun Xie ◽  
Jinlong Wang ◽  
Yongliang Guo ◽  
Chaozheng He ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Free Energy ◽  
Transition Metal ◽  
Density Functional ◽  
Reduction Reaction ◽  
Density Functional Theory Study ◽  
Free Energies ◽  
Functional Theory ◽  
Nitrogen Reduction ◽  
Single Atoms

(a) Screening results of TM@GY for the NRR based on the free energy changes of the first and last hydrogenation steps (ΔG(*N2 → *N2H) and ΔG(*NH2 → *NH3)), respectively. (b) The free energies for H and N2 adsorption on all the TM@GY.

scholarly journals DFT Comparative Study of the Formamide and Fluoro-FormamideTautomers and Their Corresponding Transition States

2021 ◽  
Author(s):  
Ashraf Mansour Al-Msiedeen
Keyword(s):  
Density Functional Theory ◽  
Free Energy ◽  
Vibrational Frequency ◽  
Density Functional ◽  
Transition States ◽  
Mulliken Charge ◽  
Free Energies ◽  
Functional Theory ◽  
The Stability ◽  
Optimized Geometries

Abstract Seventeen tautomers of formamide [NH3CO] and thirty one tautomers of fluoro-formamide [NH2FCO] were examined by density functional theory (DFT) calculations. Five methods of DFT (B3LYP/ 6-311++G, B3LYP/ 6-311++G(2df,2p), B3LYP/cc-pVTZ, wB97X-D/6-311++G(2df,2p) and wB97X-D/ cc-pVTZ) were used to calculate the energies and optimized geometries of formamide tautomers. B3LYP/cc-pVTZ method was determined as the best method and used to calculate relative energies, optimized geometries, mulliken charge distributions, Gibbs free energies and enthalpy of formations of all proposed fluoro-formamide/fluoro-formamidic acid tautomers. Ten transition states of formamide tautomers and nineteen transition states of fluoro-formamide tautomers were determined by vibrational frequency calculations (they have an imaginary value of frequency). Using B3LYP/cc-PVTZ, the relatively small energies of formamide (A1) and formamidic acid (A6) (-446246 and -446193kJ.mol -1 , respectively) participate to it being more stable than other formamide/formamidic acid tautomers, as well as for fluoro-formamide (C1) (-706947 kJ.mol -1 ) and fluoro-formamidic acid (C3) (-706855 kJ.mol -1 ). The stability of fluoro-formamide at carbonyl and at nitrogen was discussed using two thermodynamic calculations: Enthalpy of formation [∆H(298)] and Gibbs free energy (∆G) values, positive ∆G values (59 to 114 kJ mol-1) for fluoro-formamidetautomerism confirms the stability of fluoro-formamide at carbonyl.

Theoretical study on nanostructural modifications of the Si(111) surface

2019 ◽  
Vol 18 (01) ◽  
pp. 1950005
Author(s):  
Yue-Hang Dong ◽  
Xiao-Hui Liu ◽  
Wan-Sheng Su ◽  
Li-Zhen Zhao ◽  
Qing-Jun Zang ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Optical Properties ◽  
Optical Absorption ◽  
Dft Calculations ◽  
Electronic Structures ◽  
Density Functional ◽  
Theoretical Study ◽  
Surface Modifications ◽  
Thermal Stabilities ◽  
Functional Theory

Modified Si(111) surface with designed nanostructural modifications including grown pits, nanobars and nanoislands as well as deposited hill-, diamond- and cage-like nanoclusters were studied using density-functional theory (DFT) calculations. The thermal stabilities, electronic structures and optical properties of these various nanostructural modifications of the Si(111) surface were calculated and discussed. The results indicate that the optical absorption of the modified Si(111) surface can be enhanced by these surface modifications especially when depositing diamond-like nanoclusters on the surface.

A theoretical study of hybrid lead iodide perovskite homologous semiconductors with 0D, 1D, 2D and 3D structures

2017 ◽  
Vol 5 (32) ◽  
pp. 16786-16795 ◽  
Author(s):  
Jingyu Qian ◽  
Qing Guo ◽  
Leijing Liu ◽  
Bin Xu ◽  
Wenjing Tian
Keyword(s):  
Density Functional Theory ◽  
Optical Properties ◽  
Electrical Properties ◽  
Electronic Structures ◽  
Density Functional ◽  
Theoretical Study ◽  
Lead Iodide ◽  
Functional Theory ◽  
3D Structures ◽  
2D And 3D

The electrical properties, optical properties and stabilities of hybrid lead iodide perovskite homologous semiconductors with 0D, 1D, 2D and 3D structures have been investigated based on their electronic structures calculated by density functional theory (DFT).

scholarly journals A Theoretical Study of Substituted Cyclopentanones and their Enols

2003 ◽  
Vol 58 (12) ◽  
pp. 738-748 ◽  
Author(s):  
Meisa S. Al-Noeemat ◽  
Reem A. Al-Ma’ani ◽  
Salim M. Khalil
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Theoretical Study ◽  
Geometry Optimization ◽  
Density Functional Theory Calculations ◽  
Geometrical Parameters ◽  
Free Energies ◽  
Strong Electron ◽  
Functional Theory ◽  
Complete Geometry Optimization

MINDO-Forces calculations with complete geometry optimization have been performed on cyclopentanone and its enol counter part, perfluorination of cyclop entanone and its enol counterpart and X-cyclopentanones and their X-enols, where X is NO2, CF3, CN, OH, NH2 and O−. It was found that ketone is more stable than its enol counterpart. Perfluorination destabilizes ketone on the expense of enol. These results agree with the experimental results and density functional theory calculations. All substituents are destabilizing except O− in the case of cyclopentanone. It was found that NO2 and CF3 behave as strong electron withdrawing groups, CN and NC show amphielectronic behavior, and the substituents OH,NH2 and O− behave as electron releasing groups with O− being strongest. Geometrical parameters, heats of formation, entropies, and Gibbs free energies are reported

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