scholarly journals Equation of state of argon : experiments on Z, density functional theory (DFT) simulations, and wide-range model.

2012 ◽  
Author(s):  
John H. Carpenter ◽  
Seth Root ◽  
Kyle Robert Cochrane ◽  
Dawn G. Flicker ◽  
Thomas Kjell Rene Mattsson
Keyword(s):  
Density Functional Theory ◽  
Equation Of State ◽  
Density Functional ◽  
Functional Theory ◽  
Wide Range ◽  
Dft Simulations

scholarly journals Crystal structure of cobalt hydroxide carbonate Co2CO3(OH)2: density functional theory and X-ray diffraction investigation

2017 ◽  
Vol 73 (5) ◽  
pp. 868-873 ◽  
Author(s):  
Jorge González-López ◽  
Jeremy K. Cockcroft ◽  
Ángeles Fernández-González ◽  
Amalia Jimenez ◽  
Ricardo Grau-Crespo
Keyword(s):  
Crystal Structure ◽  
Density Functional Theory ◽  
Density Functional ◽  
Cobalt Hydroxide ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Cell Parameters ◽  
Wide Range ◽  
Dft Simulations

The cobalt carbonate hydroxide Co2CO3(OH)2is a technologically important solid which is used as a precursor for the synthesis of cobalt oxides in a wide range of applications. It also has relevance as a potential immobilizer of the toxic element cobalt in the natural environment, but its detailed crystal structure is so far unknown. The structure of Co2CO3(OH)2has now been investigated using density functional theory (DFT) simulations and powder X-ray diffraction (PXRD) measurements on samples synthesizedviadeposition from aqueous solution. Two possible monoclinic phases are considered, with closely related but symmetrically different crystal structures, based on those of the minerals malachite [Cu2CO3(OH)2] and rosasite [Cu1.5Zn0.5CO3(OH)2], as well as an orthorhombic phase that can be seen as a common parent structure for the two monoclinic phases, and a triclinic phase with the structure of the mineral kolwezite [Cu1.34Co0.66CO3(OH)2]. The DFT simulations predict that the rosasite-like and malachite-like phases are two different local minima of the potential energy landscape for Co2CO3(OH)2and are practically degenerate in energy, while the orthorhombic and triclinic structures are unstable and experience barrierless transformations to the malachite phase upon relaxation. The best fit to the PXRD data is obtained using a rosasite model [monoclinic with space groupP1121/nand cell parametersa= 3.1408 (4) Å,b= 12.2914 (17) Å,c= 9.3311 (16) Å and γ = 82.299 (16)°]. However, some features of the PXRD pattern are still not well accounted for by this refinement and the residual parameters are relatively poor. The relationship between the rosasite and malachite phases of Co2CO3(OH)2is discussed and it is shown that they can be seen as polytypes. Based on the similar calculated stabilities of these two polytypes, it is speculated that some level of stacking disorder could account for the poor fit of the PXRD data. The possibility that Co2CO3(OH)2could crystallize, under different growth conditions, as either rosasite or malachite, or even as a stacking-disordered phase intermediate between the two, requires further investigation.

Effect of Hf doping on He behavior in Tritium storage material ZrCo

2021 ◽  
Author(s):  
Xianggang Kong ◽  
You Yu ◽  
yanhong shen ◽  
Jiangfeng Song
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Storage Material ◽  
Functional Theory ◽  
Dft Simulations ◽  
Tritium Storage

An exhaustive analysis based on density functional theory (DFT) simulations of the effect of the Hf doping on the helium behavior has been performed in ZrCo. The He impurities have...

scholarly journals Zirconocene-Catalyzed Dimerization of α-Olefins: DFT Modeling of the Zr-Al Binuclear Reaction Mechanism

Molecules ◽  
2019 ◽  
Vol 24 (19) ◽  
pp. 3565 ◽  
Author(s):  
Ilya Nifant’ev ◽  
Alexander Vinogradov ◽  
Alexey Vinogradov ◽  
Stanislav Karchevsky ◽  
Pavel Ivchenko
Keyword(s):  
Density Functional Theory ◽  
Reaction Mechanism ◽  
Molecular Hydrogen ◽  
Density Functional ◽  
Effective Agent ◽  
Functional Theory ◽  
Dft Simulation ◽  
Dft Modeling ◽  
Dft Simulations

Zirconocene-mediated selective dimerization of α-olefins usually occurs when precatalyst (η5-C5H5)2ZrCl2 is activated by minimal excess of methylalumoxane (MAO). In this paper, we present the results of density functional theory (DFT) simulation of the initiation, propagation, and termination stages of dimerization and oligomerization of propylene within the framework of Zr-Al binuclear mechanism at M-06x/DGDZVP level of theory. The results of the analysis of the reaction profiles allow to explain experimental facts such as oligomerization of α-olefins at high MAO/(η5-C5H5)2ZrCl2 ratios and increase of the selectivity of dimerization in the presence of R2AlCl. The results of DFT simulations confirm the crucial role of the presence of chloride in the selectivity of dimerization. The molecular hydrogen was found in silico and proven experimentally as an effective agent that increases the rate and selectivity of dimerization.

Sb-terminated InAs(001)-(2×4) and (2×8) studied using scanning tunneling microscopy and ab initio density functional theory

2001 ◽  
Vol 692 ◽  
Author(s):  
William Barvosa-Carter ◽  
Frank Grosse ◽  
James H. G. Owen ◽  
Jennifer J. Zinck
Keyword(s):  
Density Functional Theory ◽  
Scanning Tunneling Microscopy ◽  
Ab Initio ◽  
Density Functional ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Functional Theory ◽  
Subsequent Formation ◽  
Wide Range ◽  
Symmetry Surface

AbstractWe have studied the structure of MBE-grown InAs(001)-(2×4) surfaces exposed to low Sb2 fluxes by scanning tunneling microscopy (STM) and ab initio density functional theory (DFT). Experimentally, we observe an Sb-terminated α2(2×4) phase over a wide range of temperatures (400–510 °C) for low Sb2 flux (<0.1 ML/s), whereas temperature and As2 flux must be carefully controlled to achieve the same As-terminated surface structure. At lower temperatures, we observe indications of an Sb-terminated (2×8) symmetry surface phase, and we report briefly on its proposed structure and stability, as well as its possible role in subsequent formation of the Sb-terminated (1×3) phase found at typical Sb2 fluxes used during heterostructure growth.

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