Search results for "functional theory"

Heterovalent BiIII/PbII ionic substitution in one-dimensional trimethylsulfoxonium halide pseudo-perovskites (X = I, Br)

2021

We report on the synthesis and characterization of novel lead and bismuth hybrid (organic-inorganic) iodide and bromide pseudo-perovskites (ABX3) containing the trimethylsulfoxonium cation (CH3)3SO+ (TMSO) in the A site, Pb/Bi in the B site, and Br or I as X anions. All of these compounds are isomorphic and crystallize in the orthorhombic Pnma space group. Lead-based pseudo-perovskites consist of one-dimensional (1D) chains of face-sharing [PbX6] octahedra, while in the bismuth-based ones, the chains of [BiX6] are interrupted, with one vacancy every third site, leading to a zero-dimensional (0D) local structure based on separated [Bi2I9]3- dimers. Five solid solutions for the iodide with di…

Uncovering the metastable γ-Ag2WO4 phase: a joint experimental and theoretical study

2017

The synthesis of metastable solid phases is a pivotal starting point for innovative materials research. Here, we report the synthesis by means of a precipitation method of the metastable cubic γ-Ag2WO4 phase under ambient conditions. Different experimental techniques such as X-ray diffraction (XRD) with Rietveld refinement, field emission scanning electron microscopy (FE-SEM), micro-Raman/ultraviolet-visible (UV-vis) diffuse reflectance, photoluminescence spectroscopies, and differential scanning calorimetry (DSC) were employed. To complement the experimental data, the geometry, morphology, vibrational and electronic structure of γ-Ag2WO4 were characterized and evaluated using first-princip…

Graph-based analysis of ethylene glycol decomposition on a palladium cluster

2017

The ethylene glycol, CH2OH-CH2OH, decomposition mechanism, occurring on a subnanometric palladium cluster shaped by 12 atoms, was investigated by means of density functional theory. Different reaction routes were identified leading to H2 and CO. The whole reaction network was analyzed, framing the results within the graph theory. The possible decomposition pathways were discussed and compared, allowing one to draw a whole picture of all the parallel, possibly competitive, routes that starting from CH2OH-CH2OH originate H2 and CO.

Editorial for PCCP themed issue "Developments in Density Functional Theory''

2016

This issue provides an overview of the state-of-the-art of DFT, ranging from mathematical and software developments, via topics in chemical bonding theory, to all kinds of molecular and material properties. Through this issue, we also celebrate the enormous contributions that Evert Jan Baerends has made to this field.

2020

The reaction of the copper(I) β-diketiminate copper complex {(Cu(BDIMes))2(μ-C6H6)} (BDIMes = N,N'-bis(2,4,6-trimethylphenyl)pentane-2,4-diiminate) with the low-valent group 13 metal β-diketiminates M(BDIDip) (M = Al or Ga; BDIDip = N,N'-bis(2,6-diisopropylphenyl)pentane-2,4-diiminate) in toluene afforded the complexes {(BDIMes)CuAl(BDIDip)} and {(BDIMes)CuGa(BDIDip)}. These feature unsupported copper-aluminum or copper-gallium bonds with short metal-metal distances, Cu-Al = 2.3010(6) A and Cu-Ga = 2.2916(5) A. Density functional theory (DFT) calculations showed that approximately half of the calculated association enthalpies can be attributed to London dispersion forces.

[3+2] Cycloaddition reaction of 1H-phosphorinium-3-olate and 1-methylphosphorinium-3-olate with methyl acrylate: A DFT study

2016

Abstract A density functional theory study was performed on the [3+2] cycloaddition (32CA) reaction of 1H-phosphorinium-3-olate and 1-methylphosphorinium-3-olate with methyl acrylate. The thermodynamic and kinetic parameters were analysed by considering the regio- and stereoisomeric pathways in gas phase and solvents. The geometries indicate that the transition states are slightly more advanced and asynchronous in ethanol. Electron localisation function topological analysis of the bonding changes along the most favourable reaction pathway associated with the 32CA reaction of 1H-phosphorinium-3-olate with methyl acrylate indicates that the reaction takes place through a two-stage one-step me…

DFT study on complete ethylene decomposition on flat and stepped Pd

2010

Abstract We applied density functional theory (DFT) calculations to study ethylidyne (CCH 3 ) adsorption and decomposition to C and H over flat and stepped Pd surfaces. Our calculations show that ethylidyne is the most stable molecule among all the possible dehydrogenation or decomposition residues of ethylene. We discuss various possible reaction pathways for ethylidyne decomposition and point out that the most probable one is via ethynyl (CCH) species suggested also by experimental observations. Our calculations indicate that the presence of steps modify the potential energy surface by increasing the binding of most of the species, and also lowering the activation barrier for several reac…

Mechanisms of covalent dimerization on a bulk insulating surface

2017

Combining density functional theory and high resolution NC-AFM experiments, we have studied the on surface reaction mechanisms' responsible for the covalent dimerization of 4-iodobenzoic acid (IBA) organic molecules on the calcite (10.4), insulating surface. When annealed at 580 K, the Molecules assemble in one-dimensional chains of covalently bound dimers: The chains have a unique orientation and result from a complex set of processes, including a nominally rather. costly double dehalogenation reaction followed by dimerization. First, focusing on the latter two processes and using the nudged elastic band method, we analyze a number of possible mechanisms involving one and two molecules, an…

Toward tailorable surfaces: a combined theoretical and experimental study of lanthanum niobate layered perovskites.

2014

A comprehensive theoretical investigation of the MLaNb2O7 (M = H, Li, Na, K, Rb, and Cs) series of ion-exchangeable layered perovskite is presented. These perovskites are in particular interesting in view of their potential applications as inorganic supports for the design of new hybrid inorganic-organic proton conductors. In particular, their structural and electronic properties have been investigated by periodic calculations in the framework of Density Functional Theory, using different exchange-correlation functionals. A general very good agreement with the available experimental (XRD, NPD, and EXAFS) data has been found. The structure of the protonated HLaNb2O7 form has also been furthe…

Towards nonlocal density functionals by explicit modelling of the exchange-correlation hole in inhomogeneous systems

2013

We put forward new approach for the development of a non-local density functional by a direct modeling of the shape of exchange-correlation (xc) hole in inhomogeneous systems. The functional is aimed at giving an accurate xc-energy and an accurate corresponding xc-potential even in difficult near-degeneracy situations such as molecular bond breaking. In particular we demand that: (1) the xc hole properly contains -1 electron, (2) the xc-potential has the asymptotic -1/r behavior outside finite systems and (3) the xc-potential has the correct step structure related to the derivative discontinuities of the xc-energy functional. None of the currently existing functionals satisfies all these re…