D-orbital Energy Level Research Articles

ジルコニウム合金の電子構造に及ぼす合金元素の影響

Alloying effects on the electronic structures were investigated for both b. c. c. Zr and h. c. p. Zr in order to obtain useful information for alloy design. The electronic structure was calculated using the DV-Xα cluster method, and two alloying parameters, the bond order Bo and the d-orbital energy level Md, were obtained for a variety of alloying elements M in Zr alloys. The binary phase diagrams of Zr-M system and crystallographic structure of Zr-M compound were found to be classfied according to the location in the Bo-Md map. Also it was shown that the activation energy for atomic diffusion could be associated with the bond order.

New crystal structure maps for intermetallic compounds

New crystal structure maps have been proposed on the basis of the molecular orbital calculations of electronic structures. Two electronic parameters have been introduced and employed as new parameters for the classification of crystal structures. One is the bond order and the other is the d-orbital energy level of elements. Both of them change following the position of elements in the periodic table. With these parameters crystal structure maps have been constructed for aluminides, silicides, and some transition-metal-based compounds. There is a clear separation of the crystal structures on the maps. These maps are found to be applicable to the prediction of crystal structures not only for binary compounds but also for ternary compounds. The possibilities of structural modification of and by alloying are also discussed with the aid of these maps.

Alloying effects on the electronic structure of chromium

Alloying effects on the electronic structure of Cr metal were investigated in order to obtain useful information for alloy design. The electronic structures were calculated by the DV - molecular orbital method, and two alloying parameters were determined theoretically. One was the d-orbital energy level Md and the other was the bond order Bo for various alloying elements M in Cr. By using these parameters, alloying behaviour was elucidated successfully. For example, the solidus temperature of binary Cr - M alloys showed a positive correlation with the bond order Bo. Also, the solubility limits of alloying elements in the Cr solid solution at 873 K were associated with Md and Bo. Furthermore, the appearance of intermetallic compounds, e.g. the -phase and the Laves phase in the Cr binary system, was predictable with these alloying parameters. The present results were shown to be useful as a guide for designing high-performance chromium-based alloys.

Electronic states of alloying elements in MoSi 2 compound

The alloying effects on the electronic structure of MoSi 2 were investigated using the DV-X α molecular orbital method. It was found that there were strong covalent SiSi and MoSi bonds in MoSi 2. The nature of the chemical bonds between atoms was modified by alloying. Two alloying parameters, the bond order Bo and the d-orbital energy level Md, were determined for various alloying elements in order to estimate the alloying behavior of MoSi 2. The solid solubilities of alloying elements in MoSi 2 could be described in terms of these two parameters. A new crystal structure map of transition metal disilicides was also made by using the Bo and the Md parameters. This map was proved to be useful in examining any possibilities of the structural modification of disilicides by alloying.

Alloying effect on the electronic structures of Nb and Mo

The alloying effects on the electronic structure were investigated for both Nb-based and Mo-based alloys in order to obtain useful information for alloy design. The electronic structure was calculated using the DV-X alpha cluster method, and two alloying parameters, the bond order BO and the d-orbital energy level MD, were obtained for a variety of alloying elements M in these metals. The binary phase diagrams of the Nb-M and Mo-M systems were found to be classified according to the location in the BO-MD map. Also, with respect to the nature of the chemical bond between atoms, Nb and Mo were compared with the other BCC metals such as Ti, V, Cr, Fe and Zr. Furthermore, it was shown that the activation energy for atomic diffusion, the heat of fusion and the melting temperature could be associated with the bond order. These results will indeed give some guide to the design of these refractory-metal-based alloys for high-temperature applications.

Evaluation of the phase stability of modified IN738LC alloys with New Phacomp

At the present time, single-crystal superalloys have the highest temperature capability and the best combination of elevated temperature properties of any structural materials and have been successfully applied as turbine airofoils. Although several special alloys suitable for single-crystal processing have been developed in recent years, only few efforts have been put into the development of so-called "hot corrosion-resistant single-crystal superalloys" which will be suitable for long-term and high-performance marine and industrial gas turbine applications. The purpose of this study is to search for the proper alloy compositions for such alloys with the guide of New Phacomp (PHAse COMPutation). This method is a newly developed alloy design concept based on DV-Xo: cluster calculations of the electronic structure of transition metals [1-3], in which Md and Bo (d-orbital energy level and bond order, respectively, of alloying transition metals) are employed as the parameters controlling the phase stability. In the alloy design process, the average values of Md and Bo are defined by taking the compositional average as

Iron-57 nuclear magnetic resonance chemical shifts of hindered iron porphyrins. Ruffling as a possible mechanism for d-orbital energy level inversion

The discrimination of binding between carbon monoxide and oxygen in heme proteins has inspired the syntheses of porphyrins with one side hindered by, e.g., a cap, a pocket, a strap, a basket handle, or some other device for the purpose of obstructing the binding of ligands to one side of the porphyrin, but the properties of these model hemes have not led to a straight-forward explanation of the natural regulatory mechanism. In this communication, the authors report that the {sup 57}Fe NMR chemical shifts are extremely sensitive to deformation of the porphyrin geometry and that novel information about the electronic levels may be extracted from investigations of substituent effects on the chemical shift within the simple framework of the Ramsey equation. In the hybrid basket-handle porphyrins, the ruffling leads to large changes in the iron d-orbital energies that may be important in understanding ligand binding in heme proteins and models.

Equilibrium phase diagram of Fe-Cr-Mn ternary system.

The isothermal phase diagram of Fe-Cr-Mn ternary system at 923 K was investigated by means of a metallographic observation, conventional X-ray diffraction and an electron probe X-ray microanalysis. In particular, attention was directed towards the phase stability of the austenite (γ) phase.The σ phase was detected even in the alloy containing 6% Cr, indicating that the γ/γ+σ phase boundary at 923 K located in the lower Cr content region of the ternary system. The γ/γ+σ phase boundary determined experimentally in low Mn alloys (up to 20 wt% Mn), was consistent with the prediction using a critical [md.gif] value of 0.89, the value chosen following our previous experiments. Here, [md.gif] is the compositional average of the Md value which is the d-orbital energy level of transition metals calculated by a molecular orbital methods. On the other hand, the γ/γ+α-Mn phase boundary appeared in the more Mn-rich alloys and moved towards the lower Mn-content region with increasing Cr content. As the result, the γ single-phase region became rather narrow. It was concluded from these results that the γ single-phase region in Fe-Cr-Mn ternary system was not so broad as was reported previously.

Nitrogen-15 and platinum-195 NMR spectra of platinum ammine complexes: trans- and cis-influence series based on platinum-195-nitrogen-15 coupling constants and nitrogen-15 chemical shifts

195Pt and 15N NMR spectra have been obtained for the series of platinum(II) complexes Pt(15NH3)3Zn+, cis-Pt(15NH3)2Z2m+, and cis-Pt(15NH3)2YZm+ (Z, Y are neutral or anionic ligands) and for the platinum(IV) complexes derived from them by peroxide oxidation, mer-Pt(15NH3)3Z(OH)2 n+ and Pt(15NH3)2Z2(OH)2 m+. From the spectra of the triammineplatinum(II) complexes, the effects on δN and 1J(Pt-N) trans and cis to Z, and on δPt, of replacing one of the ammine ligands of Pt(15NH3)4 2+ by Z were measured. With the assumption that the effects of replacing two ammine ligands are additive, the NMR parameters for diammineplatinum(II) complexes were calculated. Agreement with experimental values was good overall. NMR data for the platinum(IV) complexes were treated similarly, again with good agreement between calculated and experimental values for the diammine complexes. The influence of different ligands Z on the NMR parameters for the two different oxidation states, while generally similar, did show some consistent differences in detail. The influences of the halide ions on δPt, and on δN and J(Pt-N) trans to Z, were greater for platinum(IV) relative to platinum(II). For the series Pt(15NH3)3Zn+, results are consistent with previous generalizations, that changes in δPt mainly depend on the influence of Z on Pt 5d orbitale (through involvement in the Pt-Z σ-bond and through splitting of the d-orbital energy levels) and that changes in J(Pt-N) trans to Z depend mainly on variations in the Pt 6s contribution to the Pt-N bond. δN trans to Z shows an inverse linear correlation with δPt. Cis influences on δN and J(Pt-N) are smaller than trans influences but are still significant.

ChemInform Abstract: THE CIRCULAR DICHROISM AND MAGNETIC CIRCULAR DICHROISM SPECTRA OF BIS(STILBENEDIAMINE)NICKEL(II) COMPLEXES

The temperature dependence of the absorption and circular dichroism spectra for [Ni((+)-stien)2](ClO4)2 is indicative of the equilibrium between the square planar (yellow) and tetragonal (violet) species in acetone solutions. On the other hand, the square planar species is predominant in a methanol solution, even at room temperature, in the case of [Ni(meso-stien)2](ClO4)2. The Cl− as a counter anion favored an equilibrium slightly displaced to the tetragonal species. The analysis of the CD and MCD bands suggests an ordering of the d-orbital energy levels of dx2–y2>>dz2>dxz,dyz>dxy.

The Circular Dichroism and Magnetic Circular Dichroism Spectra of Bis(stilbenediamine) nickel(II) Complexes

Abstract The temperature dependence of the absorption and circular dichroism spectra for [Ni((+)-stien)2](ClO4)2 is indicative of the equilibrium between the square planar (yellow) and tetragonal (violet) species in acetone solutions. On the other hand, the square planar species is predominant in a methanol solution, even at room temperature, in the case of [Ni(meso-stien)2](ClO4)2. The Cl− as a counter anion favored an equilibrium slightly displaced to the tetragonal species. The analysis of the CD and MCD bands suggests an ordering of the d-orbital energy levels of dx2–y2>>dz2>dxz,dyz>dxy.

The assignment of the electronic spectra of nickel(II) complexes with non-conjugating sulphur-containing ligands

The polarised crystal and solutions, electronic spectra of some quadratic dithiocarbomate and related nickel(II) complexes have been measured. In the cases where alignments of the molecules are favourable, Ni(S 2P(OC 2H 5) 2) 2 and Ni(s 2CN(n-C 3H 7) 2) 2, a reasonable assignment of the bands occurring between 14 and 28 kK as being all due to « dd » transitions, is possible. The separation of the four d-orbital energy levels is thus much greater than that in analogous oxygen and nitrogen containing complexes. Assignments in both D 2h and D 2 points groups are possible, and reasons are given for preferring the latter. Because the selection rules in both cases do not allow a distinction to be made between the d z2→d xy and d x2−y2→d xy transition, either order: d xy>d x2−y2> or <d z2>d xz>d yz, is possible. Ni(S 2P(C 6H 5) 2) 2 gives an electronic spectrum also showing two bands between 26 kK and 28 kK which may ascribed to the d xz→d xy and d yz→d xy transitions. This appears to be the first square planar nickel(II) complex to show four probably singlet-singlet bands in its electronic spectrum. These further bands are not easily identified in the other complexes because of the presence of nearby charge transfer absorption. The behaviour of the band energies on changes in the Ni-S distances is described and discussed.

Visible Absorption Spectra of Copper-ethylene-diamine-bis(acetylacetone) in the Crystalline State

FOR square planar copper complexes the crystal field theory predicts a splitting of the five-fold degenerate d-orbital energy-levels into four energetically different levels, d xy, d z 2, d x 2–y 2, and d zx(d yz), in the order of diminishing energy1. The visible absorption in these systems is associated with the transitions from d Zx to d xy (w 1, from d x 2–y 2 to d xy (w 2)and from d z 2 to d xy (w 3), where w 1 is the shortest wave-length and w 3 the longest wave-length band with w 2 in between. The absorption spectra of square planar copper complexes in solution invariably consist of one broad absorption band in the visible region, which, however, could be resolved into three component bands by Gaussian analysis2. With the object of finding if these split levels could be detected in the absorption spectra of the single crystal of a square planar copper complex, the present investigation was undertaken on the absorption spectra of an elongated platelet of copper-ethylene-diamine-bis(acetylacetone).