Hybridization Of Valence Electrons Research Articles

Investigation of the formation of the electron structure of metallocarbonic nanoforms

Model samples of nanostructures are synthesized with the use of transition metals, with a different number of d electrons and sp elements of groups II and III with a different number of valence p electrons, as modifiers. The activity of nanostructure synthesis is investigated depending on the addition of sp elements. A procedure is developed for determining the atomic magnetic moment of the d metals and the change in the distances between atoms of the metal and the sp element via the parameters of the X-ray photoelectron spectrum of transition metals, which allows the degree of hybridization of valence electrons in the chemical bond of adjacent atoms (Me-X) to be determined. As a result of the investigation the laws of nanoform growth are found which facilitate the development of new directions in the synthesis of nanostructures with unique properties.

Phase stability comparison by first principle calculation and experimental observation of microstructure evolution in a Mg–6Gd–2Zn(wt%) alloy

The microstructure of a Mg–6Gd–2Zn(wt%) alloy was investigated by SEM and TEM observations; phase stability comparison was performed by first principle calculation. The long periodic structure (LPS) was found to be transformed from the Mg 3Gd phase when subjected to solution treatment at 723 K for 6 h plus aging treatment at 633 K for 8 h. When aged at 503 K for 36 h after solution treatment, the LPS phase transformed to the much more stable Mg 3Gd phase. The calculations of cohesive energy and formation enthalpy shown that the Mg 3Gd phase is more stable in comparison with the LPS phase; the analyses on DOS (density of states) distributions proved that Zn alloying makes the LPS phase less stable due to p– d hybridization of valence electrons.

Cluster structure of the surface in the amorphous, quasicrystalline, and liquid states

The electronic structure of the Zr60Ni20Ti20, Al65Cu20Fe15, and Al86Mn14 systems has been investigated by X-ray photoelectron spectroscopy and band calculations of the total and partial densities of electronic states have been carried out by the TB-LMTO-ASA method with the aim of studying the chemical bonds and the nearest environment of atoms in the liquid, amorphous, and quasicrystalline states. A direct proof of the inheritance of the chemical structure of the liquid state in the amorphous and quasicrystalline states has been obtained for the first time. The similarity of the electronic structure and the nearest environment of atoms indicates identity of clusters in the liquid, amorphous, and quasicrystalline states. The degree of hybridization of valence electrons of atoms in clusters increases in going from the quasicrystalline to the amorphous state due to the increase the number of transition metal atoms in clusters.

A new study on the catalytic mechanism of Fe-based alloys in diamond formation by Mössbauer spectroscopy

Mossbauer spectroscopy has been used to systemically study the catalytic mechanism of Fe-based alloys in diamond formation at high temperature–high pressure (HTHP) for the first time. Mossbauer spectra reveal the magnetic state of the 3d electrons of a Fe atom in the Fe-based alloy catalyst during diamond formation at HTHP. During carburization at lower temperatures than that required for diamond formation and diamond formation in the diamond-stability region using Fe-based alloys as a catalyst, both the quadrupole splitting QS and the isomer shift IS change from negative to positive, especially reaching a state in which they are zero. It was indicated that the state of the 3d-shell electrons of the iron atom changes greatly during carburization and diamond formation and that the incomplete 3d sub-bands of Fe atoms in the catalyst alloys could be filled up in proper order by electrons of interstitial carbon atoms. During diamond formation, the unpaired 3d-shell electrons of an iron atom in the Fe-based alloy absorb and interact with 2Pz electrons of the carbon atoms. There exist a Fe–C bonding and an electron charge transfer stage. The 2Pz electrons of the carbon atoms could be dragged into the metal atoms in the catalyst alloy and would make a transition of triangular (sp2π) hybridization of valence electrons to tetrahedral (sp3) hybridization of valence electrons (a transition of sp2π bonds of graphite to sp3 bonds of diamond), resulting in a transition of graphite structure to diamond. Although the conclusion of this study is strictly applicable only to Fe-based alloy catalysts, it could be considered more general because of the chemical similarities between the transition elements used as solvent catalysts for diamond synthesis.

Photo-thermal excitation gas-source MBE growth of super-doped Si:Mn for spin-photonics applications

Crystalline Si thin films doped with transition metal elements far beyond the solid solubility are named here as ‘super-doped Si:TM’ (TM=transition metals). Super-doped Si:Mn thin films with doping levels of more than 10% have been grown by using a photo-thermal excitation gas-source molecular beam epitaxy (GSMBE) technique. The GSMBE apparatus used here was equipped with a ‘hot W-filament cell’, and hence it is called photo-thermal excitation GSMBE. The hot W-filament cell decomposed quite effectively the source of SiCl2H2 molecules and enabled the growth of polycrystalline super-doped Si:Mn solid-solution films at substrate temperatures as low as 300°C. Auger electron spectroscopy has revealed the characteristic valence electron spectra arising from the valence-electron hybridization between 3d electrons of Mn and s–p electrons of Si.

Friction and wear behaviour of hard and superhard coatings at cryogenic temperatures

The work presents data on friction and wear behaviour of pin-on-disc pairs with superhard diamond-like carbon (DLC) coatings and hard coatings of zirconium nitride (ZrN) and titanium nitride (TiN) in liquid nitrogen with loads of 2.5 and 10 N and sliding speed of 0.06 m/s. It is shown that at cryogenic temperatures the friction coefficients of pairs of two types of DLC coatings obtained by vacuum-arc deposition of filtered high-speed carbon plasma fluxes depend to a great deal on the mechanical properties of the coatings defined by predominant sp 2 or sp 3 hybridization of valence electrons. A friction coefficient of 0.76 was observed for friction pairs of superhard (90 GPa) DLC coatings having properties similar to those of diamond. For “softer” DLC coatings of 40 GPa and properties similar to those of graphite the friction coefficient shows lower values (0.24–0.48) dependent on normal load and counterbody material. The DLC coatings obtained by the filtered arc technology exhibit good wear resistance and have strong adhesion to the substrate under friction in liquid nitrogen. With a normal load of 10 N under cryogenic temperature a low wear rate (of the order of 7.2×10 −4 nm/cycle) was found for superhard DLC coatings. The friction coefficient of pairs with hard ZrN and superhard DLC coatings on steel discs was revealed to be linearly dependent on the counterbody material hardness between 20 and 100 GPa. The hardness of the pin was varied by means of depositing TiN or DLC coatings and also by using high-hardness compounds (boron nitride and synthetic diamond). Proceeding this way can be promising since it offers the possibility of creating low-temperature junctions of required friction properties.

Growth and properties of super-doped Si : Mn for spin-photonics

Si thin films doped heavily with transition-metal elements, manganese (Mn), at the doping levels more than 5% have been prepared. These films that contain Mn far beyond the solubility limit are named “super-doped Si : Mn”. The gas-source molecular beam epitaxy technique enables us to grow super doped Si : Mn at low substrate temperatures as low as 300°C by using photo-thermal excitation molecular beam cells developed in this study. Auger electron spectroscopy has revealed the characteristic valence spectra arising from the valence-electron hybridization between 3d electrons of Mn and s–p electrons of Si. So-called anomalous Hall effect has also been observed around 70 K in Si : Mn samples, which suggests the presence of internal magnetic field due to the magnetization of local Mn spins in Si.

Influence of structural defects on the intensity of carbon emission spectra

The influence of atomic ordering defects on the integrated characteristics of photoelectron and Auger spectra of various carbon objects is studied. The analysis of the data indicates that there is a correlation between the type of hybridization of valence electrons and the relative intensity of photoemission of the core electrons and Auger emission. The results obtained on a fullerene sample support the existence of fractional types of hybridization.

Electron-transfer thermodynamics, valence-electron hybridization, and bonding of the meso-tetrakis(2,6-dichlorophenyl)porphinato complexes of manganese, iron, cobalt, nickel, copper, silver, and zinc and of the P+Mn(O) and .bul.P+Fe(O) oxene adducts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectron-transfer thermodynamics, valence-electron hybridization, and bonding of the meso-tetrakis(2,6-dichlorophenyl)porphinato complexes of manganese, iron, cobalt, nickel, copper, silver, and zinc and of the P+Mn(O) and .bul.P+Fe(O) oxene adductsHui Chan Tung, Pipat Chooto, and Donald T. SawyerCite this: Langmuir 1991, 7, 8, 1635–1641Publication Date (Print):August 1, 1991Publication History Published online1 May 2002Published inissue 1 August 1991https://doi.org/10.1021/la00056a015RIGHTS & PERMISSIONSArticle Views148Altmetric-Citations9LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (754 KB) Get e-Alerts Get e-Alerts

Electron-Transfer Thermodynamics, Valence-Electron Hybridization, and Bonding for Iron Compounds

Abstract The electron-transfer thermodynamics (a) for iron compounds (FeXm) and complexes (FeLn) and (b) for their heteroatoms (X/X−) and ligands (L/L−) in combination with other physical data provide insight into the valence-electron hybridization and bonding of the iron center. The basic conclusions are: (a) the chemical bonding of iron in its compounds and complexes is covalent and similar to that of carbon. (b) the electron-transfer processes of iron complexes are ligand-centered, and (c) the iron-ligand covalent bond energies can be evaluated from the electrochemically determined redox thermodynamics.

X-ray emission spectra and electronic structure ZrV2 and ZrV2Dx

Abstract The Lα and Kβ 5 X-ray emission spectra ( L III - M IV , V and K - N II , III transitions respectively) of vanadium and the Lβ 2, 15 X-ray emission spectra ( L III - N IV , V transition) of zirconium in the compounds ZrV 2 and ZrV 2 D x ( x = 2;4.8) have been studied. The spectra have been found to exhibit a sharp concentration dependence: with increase in deuterium content a low-energy band shows up which arises from the D1 s -Mep, d hybridization of valence electrons. As the temperature is decreased from 300 to 100 K the shape of the spectra changes, which is apparently due to low-temperature structural transformations.