Izaak Williamson

Reference Diffraction Patterns, Microstructure, and Pore-Size Distribution for the Copper (II) Benzene-1,3,5-Tricarboxylate Metal Organic Framework (Cu-BTC) Compounds

Cu-paddle-wheel-based Cu 3 (BTC) 2 (nicknamed Cu-BTC, where BTC ≡ benzene 1,3,5-tricarboxylate) is a metal organic framework (MOF) compound that adopts a zeolite-like topology. We have determined the pore-size distribution using the Gelb and Gubbins technique, the microstructure using small-angle neutron scattering and (ultra) small-angle X-ray scattering (USAXS\SAXS) techniques, and X-ray powder diffraction reference patterns for both dehydrated d -Cu-BTC [Cu 3 (C 9 H 3 O 6 ) 2 ] and hydrated h -Cu-BTC [Cu 3 (C 9 H 3 O 6 ) 2 (H 2 O) 6.96 ] using the Rietveld refinement technique. Both samples were confirmed to be cubic Fm

Improved thermoelectric performance of (Fe,Co)Sb3-type skutterudites from first-principles

\bar 3

Carbon Dioxide Sorption in a Nanoporous Octahedral Molecular Sieve

m (no. 225), with lattice parameters of a = 26.279 19(3) A, V = 18 148.31(6) A 3 for d -Cu-BTC, and a = 26.3103(11) A, and V = 18 213(2) A 3 for h -Cu-BTC. The structure of d -Cu-BTC contains three main pores of which the diameters are approximately, in decreasing order, 12.6, 10.6, and 5.0 A. The free volume for d -Cu-BTC is approximately (71.85 ± 0.05)% of the total volume and is reduced to approximately (61.33 ± 0.03)% for the h -Cu-BTC structure. The d -Cu-BTC phase undergoes microstructural changes when exposed to moisture in air. The reference X-ray powder patterns for these two materials have been determined for inclusion in the Powder Diffraction File.

Thermodynamic stability of a bi-layer of copper nitride on Cu(100) surface

Skutterudite materials have been considered as promising thermoelectric candidates due to intrinsically good electrical conductivity and tailorable thermal conductivity. Options for improving thermal-to-electrical conversion efficiency include identifying novel materials, adding filler atoms, and substitutional dopants. Incorporating filler or substitutional dopant atoms in the skutterudite compounds can enhance phonon scattering, resulting in reduction of thermal conductivity, as well as improving electrical conductivity. The structures, electronic properties, and thermal properties of double-filled Ca0.5Ce0.5Fe4Sb12 and Co4Sb12−2xTexGex compounds (x = 0, 0.5, 1, 2, 3, and 6) have been studied using density functional theory-based calculations. Both Ca/Ce filler atoms in FeSb3 and Te/Ge substitution in CoSb3 cause a decrease in lattice constant for the compounds. As Te/Ge substitution concentration increases, lattice constant decreases and structural distortion of pnictogen rings in the compounds occurs....

Electronic structure, pore size distribution, and sorption characterization of an unusual MOF, {[Ni(dpbz)][Ni(CN)4]}n, dpbz = 1,4-bis(4-pyridyl)benzene

We have performed first-principles density functional theory calculations, incorporated with van der Waals interactions, to study CO2 adsorption and diffusion in nanoporous solid—OMS-2 (Octahedral Molecular Sieve). We found the charge, type, and mobility of a cation, accommodated in a porous OMS-2 material for structural stability, can affect not only the OMS-2 structural features but also CO2 sorption performance. This paper targets K+, Na+, and Ba2+ cations. First-principles energetics and electronic structure calculations indicate that Ba2+ has the strongest interaction with the OMS-2 porous surface due to valence electrons donation to the OMS-2 and molecular orbital hybridization. However, the Ba-doped OMS-2 has the worst CO2 uptake capacity. We also found evidence of sorption hysteresis in the K- and Na-doped OMS-2 materials.

Structural, Electrical, Phonon, and Optical Properties of Ti- and V-Doped Two-Dimensional MoS 2

Ultrathin insulating films composed of a few atomic layers are being extensively used for controlling the electronic coupling of nanostructures deposited on a substrate. Ultrathin film, for example, a single layer of Cu(2)N deposited on a Cu(100) surface (known as Cu(2)N/Cu(100) surface) has been used to determine the spectral properties of nanomagnets using scanning tunneling spectroscopy. However, recent experiments that measure spin relaxation times in a single atom suggest that the single layer of Cu(2)N does not provide efficient electronic decoupling. In this work, we study the thermodynamic stability of a bi-layer of copper nitride on the Cu(100) surface. We calculate adsorption and co-adsorption energies of Cu and N as a function of their concentration on the Cu(2)N/Cu(100) surface using density functional theory. We find that the adsorption and co-adsorption energies of Cu and N on the Cu(2)N/Cu(100) surface are of the order of a few eV. This suggests that the bi-layer of copper nitride is thermodynamically stable on the Cu(100) surface. We also find that the work function of N-adsorbed Cu(2)N/Cu(100) increases with the N concentration, suggesting a better insulating character of the bi-layer of copper nitride on the Cu(100) surface.

First-principles studies of carbon dioxide adsorption in cryptomelane/hollandite-type manganese dioxide

The monoclinic (Ni(L)[Ni(CN)4] (L= 1,4-Bis(4-pyridyl) benzene) compound (defined as Ni-dpbz) is a flexible metal organic framework which assumes a pillared structure with layers defined by 2D Ni[Ni(CN)4]n nets and dpbz ligands as pillars. The structure features an entrapped dpbz ligand that links between the open ends of four-fold Ni sites from two neighboring chains. This arrangement results in an unusual 5-fold pseudo square-pyramid environment for Ni and a significantly long Ni-N distance of 2.369(4) A. Using Density Functional Theory calculations, the different bonding characteristics between the 5-fold and 6-fold Nis were determined. We found that there is weak covalent bonding between the 5-fold Ni and N in the entrapped ligand, and the 6-fold Ni-N bonds provide effective electronic conduction. The disordered dimethyl sulfoxide (DMSO) solvent molecules are not bonded to the framework. The material has a single pore with a diameter of 4.1 A. This pore includes approximately 55% of the total free volume (based on a zero-diameter probe). The accessible pore surface area and pore volume were calculated to be 507 m2/g and 6.99 cm3/kg, respectively. The maximum amount of CO2 that can be accommodated in the pores after DMSO is removed was found to be 204 mg/g, agreeing with the results of adsorption/desorption experiments of about 220 mg/g.The monoclinic (Ni(L)[Ni(CN)4] (L= 1,4-Bis(4-pyridyl) benzene) compound (defined as Ni-dpbz) is a flexible metal organic framework which assumes a pillared structure with layers defined by 2D Ni[Ni(CN)4]n nets and dpbz ligands as pillars. The structure features an entrapped dpbz ligand that links between the open ends of four-fold Ni sites from two neighboring chains. This arrangement results in an unusual 5-fold pseudo square-pyramid environment for Ni and a significantly long Ni-N distance of 2.369(4) A. Using Density Functional Theory calculations, the different bonding characteristics between the 5-fold and 6-fold Nis were determined. We found that there is weak covalent bonding between the 5-fold Ni and N in the entrapped ligand, and the 6-fold Ni-N bonds provide effective electronic conduction. The disordered dimethyl sulfoxide (DMSO) solvent molecules are not bonded to the framework. The material has a single pore with a diameter of 4.1 A. This pore includes approximately 55% of the total free vol...