Search results for "ELECTRONIC STRUCTURE"
showing 10 items of 722 documents
Quaternary Heusler Compounds without Inversion Symmetry: CoFe 1+ x Ti 1– x Al and CoMn 1+ x V 1– x Al
2011
We report the quaternary Heusler compound derivatives CoFe1+xTi1–xAl and CoMn1+xV1–xAl, which do not have centers of inversion. Classical T2T′M (T, T′ = transition metal, M = main group element) Heusler compounds (prototype: Cu2MnAl) crystallize in the L21 structure, space group Fmm (225) that exhibits a center of inversion. Replacing one of the T2 atoms by another transition element (T″) results in a quaternary TT′T″M compound with F3m symmetry (Y; structure type LiMgPdSn) without center of inversion. In the case of “quasi closed shell” compounds with 24 valence electrons in the primitive cell, one expects the absence of ferromagnetism according to the Slater–Pauling rule. Increasing the n…
Solution Chemistry of Element 106: Theoretical Predictions of Hydrolysis of Group 6 Cations Mo, W, and Sg
2001
Fully relativistic molecular density-functional calculations of the electronic structure of hydrated and hydrolyzed complexes have been performed for the group 6 elements Mo, W, and element 106, Sg. By use of the electronic density distribution data, relative values of the free energy changes and constants of hydrolysis reactions were defined. The results show hydrolysis of the cationic species with the formation of neutral molecules to decrease in the order Mo > W > Sg, which is in agreement with experiments for Mo, W, and Sg. For the further hydrolysis process with the formation of anionic species, the trend is reversed: Mo > Sg > W. A decisive energetic factor in the hydrolysis process …
A black-box approach to the construction of metal-radical multispin systems and analysis of their magnetic properties
2020
An interaction of M(hfac)2 (M = Mn or Ni) with N-(bis(4,4,5,5-tetramethyl-3-oxido-1-oxyl-4,5-dihydro-1H-imidazol-2-yl)methylene)-2-methyl-propan-2-amine oxide (a nitronyl nitroxide diradical with theC[double bond, length as m-dash]N(O)-tert-Bu coupler) was investigated under various conditions. It was found that prolongation of reaction time caused transformation of the initial diradical into new diradicals with the uniqueC[double bond, length as m-dash]N-OH coupling unit and formation of binuclear Mn(ii) and Ni(ii) complexes, which were characterized by X-ray diffraction analysis. The resulting binuclear heterospin complexes have a complicated magnetic structure with six paramagnetic cente…
Magnetic and Structural Properties of Heusler Compounds with 27.8 Valence Electrons
2010
Co2-based Heusler compounds with 27.8 valence electrons exhibit an exceptional electronic structure that makes them interesting materials for the application in spintronics. Co2Cr0.6Fe0.4Al is the most prominent example of this particular family of compounds. In this article new materials of this class are tested with respect to their structural and magnetic properties. X-ray diffraction, Mossbauer spectroscopy, energy dispersive X-ray spectroscopy, and SQUID magnetometry were carried out to characterize the compounds. The use of Co2Fe0.45Ti0.55Ge as a new material in spintronic devices is suggested.
Computational strategies to model the interaction and the reactivity of biologically-relevant transition metal complexes
2022
Abstract Transition metal atoms possess the unique capacity to induce significant changes in the electronic structure of their ligands, often culminating in substantial modification of their chemical behavior, and this ability explains well their evolutionary incorporation into the living matter. Exactly this complexity of metal atom behaviours on the electronic level is the reason of various quantum chemistry strategies have been developed for their description. On the other hand, the application of quantum chemistry methodologies to gain a comprehensive understanding of the interaction between metal and biological matter, can only be approached through adequate modelling of the chemical p…
Emission energy of azole-based ionic iridium(III) complexes: a theoretical study.
2014
A theoretical density functional theory study has been performed on different families of cationic cyclometallated Ir(III) complexes with the general formula [Ir(C^N)2(N^N)](+) and azole-based ligands. The goal was to investigate the effect that the number and position of the nitrogen atoms of the azole ring have on the electronic structure and emission wavelength of the complex. The increase in the number of nitrogen atoms changes the relative energy of the HOMO and LUMO levels and leads to a gradual shift in the emission wavelength that can be larger than 100 nm. The direction of the shift however depends on the ligand in which the azole ring is introduced. The emission shifts to bluer wa…
Towards a better understanding of honeycomb alternating magnetic networks.
2015
Two new two-dimensional homometallic compounds {[M2(bpm)(ox)2]n·5nH2O} with M = Co(II) (1) and Zn(II) (2) and the mononuclear nickel(II) complex [Ni(bpm)2(ox)]·2H2O (3) [bpm = 2,2'-bipyrimidine and ox = oxalate] have been prepared and structurally characterized. 1 and 2 are isostructural compounds whose structures are made up of oxalate-bridged M(II) cations cross-linked by bis-bidentate bpm molecules to afford a honeycomb layered network extending in the crystallographic ab plane. The layers are eclipsed along the crystallographic c axis and show graphitic-like interactions between the bpm rings. The three-dimensional supramolecular network deriving from such interactions is characterized …
Au70S20(PPh3)12: an intermediate sized metalloid gold cluster stabilized by the Au4S4 ring motif and Au-PPh3 groups
2018
Reducing (Ph3P)AuSC(SiMe3)3 with L-Selectride® gives the medium-sized metalloid gold cluster Au70S20(PPh3)12. Computational studies show that the phosphine bound Au-atoms not only stabilize the electronic structure of Au70S20(PPh3)12, but also behave as electron acceptors leading to auride-like gold atoms on the exterior.
A two-dimensional radical salt based upon BEDT-TTF and the dimeric, magnetic anion [Fe(tdas)2]22−: (BEDT-TTF)2[Fe(tdas)2] (tdas = 1,2,5-thiadiazole-3…
2002
In an attempt to synthesize new synthetic metals which couple magnetic properties to conductivity, we prepared the novel salt (BEDT-TTF)2[Fe(tdas)2] [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene, hereafter referred to as ET; tdas = 1,2,5-thiadiazole-3,4-dithiolate] by the electrocrystallization technique. The crystal structure of this compound, as determined by single crystal X-ray diffraction, contains conducting, organic ET layers separated by dimerized, magnetic [Fe(tdas)2]22− anions. Due to the magnetic insulating ground electronic state of the ET layer, thermally activated conductivity is observed, with a room temperature value of about 1 S cm−1. This salt was also characterized by…
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 …