Search results for "Density Functional Theory."
showing 10 items of 935 documents
Spectroscopic, density functional theory, nonlinear optical properties and in vitro biological studies of Co(II), Ni(II), and Cu(II) complexes of hyd…
2021
Density functional theory based screening of ternary alkali-transition metal borohydrides: a computational material design project.
2009
We present a computational screening study of ternary metal borohydrides for reversible hydrogen storage based on density functional theory. We investigate the stability and decomposition of alloys containing 1 alkali metal atom, Li, Na, or K M1; and 1 alkali, alkaline earth or 3d / 4d transition metal atom M2 plus two to five BH4 groups, i.e., M1M2BH42‐5, using a number of model structures with trigonal, tetrahedral, octahedral, and free coordination of the metal borohydride complexes. Of the over 700 investigated structures, about 20 were predicted to form potentially stable alloys with promising decomposition energies. The M1Al/ Mn/ FeBH44, Li/ NaZnBH43, and Na/ KNi/ CoBH43 alloys are …
Molybdenum Clusters on a TiO2(110) Substrate Studied by Density Functional Theory.
2009
International audience; A theoretical study on molybdenum clusters adsorbed on a rutile TiO2(110) substrate is reported. Using density functional theory, equilibrium geometries, atomic charges, and total energies have been calculated for clusters containing up to five Mo atoms. Isolated Mo adatoms are strongly oxidized and repel each other. The Mo oxidation state is considerably lowered as soon as the first short Mo−Mo bond is formed. The relative stability of different cluster geometries can be understood from the competition between Mo−Mo and Mo−O bonding. Some low-energy structures for two and three Mo atoms involve large displacements of a substrate oxygen atom. The most stable five-ato…
A theoretical study on the thermal ring opening rearrangement of 1H-bicyclo[3.1.0]hexa-3,5-dien-2-one: a case of two state reactivity
2009
The molecular mechanism of the thermal rearrangement of singlet 1H-bicyclo[3.1.0]hexa-3,5-dien-2-one to give triplet 4-oxocyclohexa-2,5-dienylidene has been investigated using density functional theory (B3LYP and M05-2X functionals) as well as ab initio CASSCF and CASPT2 multiconfigurational methods. The reactant has a singlet ground state while the product can be found in three low lying electronic states P((3)B(1)), P((1)B(1)), and P((1)A'). Therefore, the molecular mechanism of this ring opening rearrangement may involve up to three different potential energy surfaces of two spin multiplicities: two singlet (closed shell, CS, and open shell, OS) and one triplet. The stationary points on …
Analysis of Localized Surface Plasmon Resonances in Spherical Jellium Clusters and Their Assemblies
2017
Due to multiple possible applications of physico-chemical properties of plasmonic metal nanoparticles and particle systems, there is high interest to understand the mechanisms that underlie the birth of localized surface plasmon resonance (LSPR). Here we studied the birth of the LSPR in spherical jellium clusters with the density of sodium and with 8, 20, 34, 40, 58, 92, 138, and 186 electrons, by using the linear response time-dependent density functional theory (lr-TDDFT). The coupling of the individual plasmon resonances in dimer, trimer, tetramer, and hexamer cluster assemblies consisting of the 8-electron cluster was also studied. The Kohn-Sham electron-hole transitions contributing to…
Unraveling the LiNbO3 X-cut surface by atomic force microscopy and density functional theory
2014
The ${\text{LiNbO}}_{3}$(2$\overline{1}\overline{1}0$) surface, commonly referred to as X-cut, is investigated by means of atomic force microscopy and first-principles calculations. Atomically resolved atomic force microscopy images show geometrical patterns not compatible with truncated bulk terminations. Fast Fourier transformation of the real-space images shows an oblique surface unit cell with lattice parameters of $a=0.75\ifmmode\pm\else\textpm\fi{}0.02$ nm, $b=0.54\ifmmode\pm\else\textpm\fi{}0.02$ nm, and $\ensuremath{\alpha}=94.{8}^{\ensuremath{\circ}}$. Comparing these experimental results with the theoretical models of stable surface terminations provides clear evidence for the for…
Teaching Inorganic Photophysics and Photochemistry with Three Ruthenium(II) Polypyridyl Complexes: A Computer-Based Exercise
2015
Among computational methods, DFT (density functional theory) and TD-DFT (time-dependent DFT) are widely used in research to describe, inter alia, the optical properties of transition metal complexes. Inorganic/physical chemistry courses for undergraduate students treat such methods, but quite often only from the theoretical point of view. In the calculation exercise herein described, students are guided step by step through the computational study of the photophysics and photochemistry of polypyridyl Ru(II) d6-metal complexes. In particular, by means of DFT and TD-DFT calculations, they are asked to examine and interpret a set of experimental data describing the absorption, emission, and ph…
Novel structural phases and the properties of LaX (X = P, As) under high pressure: first-principles study
2020
The particle swarm optimization algorithm and density functional theory (DFT) are extensively performed to determine the structures, phase transition, mechanical stability, electronic structures, and thermodynamic properties of lanthanide phosphates (LaP and LaAs) in the pressure range of 0 to 100 GPa. Two novel high-pressure structures of LaP and LaAs are first reported here. It is found that LaX (X = P, As) undergo a phase transition from NaCl-type structure (Fm3m) to CsCl-type structure (P4/mmm) at 19.04 GPa and 17.22 GPa, respectively. With the elevation of the pressure, C2/m-LaP and Imma-LaAs are the most stable structures up to 70.08 GPa and 85.53 GPa, respectively. Finally, the analy…
DFT study of a singleF center in cubic SrTiO3 perovskite
2006
Various properties of a cubic phase of SrTiO3 perovskite containing single F centers (neutral oxygen vacancies), including energies of their formation and migration, were simulated using different formalisms of density functional theory (DFT) as implemented into CRYSTAL-2003 and VASP computer codes. The lattice relaxation around the F center was found to be sensitive to both shape and size of supercells used. The larger the supercell, the closer the defect energy level in the bandgap lies to the conduction band bottom. It approaches the optical ionization energy of 0.49 eV for 270- and 320-atom supercells, where the distance between neighboring defects increases up to four lattice constants…
Excited state decay of cyclometalated polypyridine ruthenium complexes: insight from theory and experiment.
2016
Deactivation pathways of the triplet metal-to-ligand charge transfer ((3)MLCT) excited state of cyclometalated polypyridine ruthenium complexes with [RuN5C](+) coordination are discussed on the basis of the available experimental data and a series of density functional theory calculations. Three different complex classes are considered, namely with [Ru(N^N)2(N^C)](+), [Ru(N^N^N)(N^C^N)](+) and [Ru(N^N^N)(N^N^C)](+) coordination modes. Excited state deactivation in these complex types proceeds via five distinct decay channels. Vibronic coupling of the (3)MLCT state to high-energy oscillators of the singlet ground state ((1)GS) allows tunneling to the ground state followed by vibrational rela…