Valence electron structures dependences of structural stability and properties of REX_(3)(RE=rare earth;X=In,Tl)and RE(In,Co)3 alloys

Intermetallic compounds REIn3(RE=rare earth)have attracted much attention due to their unique characteristics:crystal field effect,Kondo effect,superconductivity,heavy fermion,and antiferromagnetism,and their cobalt diluted alloys exhibit the ferromagnetic half-metallic characteristics at room temperature.In this study,an empirical electron theory(EET)is employed to investigate systemically the valence electronic structure,the thermal and magnetic properties of REX_(3) and their cobalt diluted alloys for revealing the mechanism of physical properties.The calculated bond length,melting point,and magnetic moment match the experimental ones very well.The study reveals that structural stability and physical properties of REX_(3) and their cobalt dilute alloys are strongly related to their valence electron structures.It is suggested that the structural stability and cohesive energy depend upon the covalent electron,the melting point is modulated by covalent electron pair,and the magnetic moment is originated from 3d magnetic electron.The ferromagnetic characteristics of Co-diluted REIn3 alloys is originated from the introduction of strong ferromagnetic Co atom,but,a competition is caused between the electron transition from valence electron to magnetic electron on d orbit and its reversal electron transformation with increasing the content of cobalt,which results in the formations of diluted magnetic Gd(In,Co)3 alloy with minor amount of cobalt and strong magnetic Nd(In,Co)3 alloy with doping more Co atoms.

Effect of Valence Electron Structure on Temper Process and Hardness of the Supersaturated Carburized Layer

By measuring the hardness of carburized layer of a new type supersaturated carburizing steel （35Cr3SiMnMoV） at different temper temperature for 2 h, the relationship curve between the carburized layer hardness and the temper temperature is established. The result indicates that the hardness goes down firstly, then up and down, just like a wave consistent with the temperature increase. A secondary hardening peak appears at 570 ℃ or so. Based on Empirical Election Theory （EET） of Solids and Molecules, the valence electron structures （VESs） containing α-Fe-C, α-Fe-C-Me segregation structure units and carbide are calculated. The laws of temper process and hardness change with the temper temperature are explained, and the fact that reconstruction of θ-Fe3C is prior to that of special carbide at high tempering is analyzed with the phase structure formation factor, S, being taken into consideration. Therefore, the laws of temper process and hardness change of supersaturated carburized layer at different temper temperature can be traced back to valence electron structure （VES） level of alloy phase.

A Valence Electron Structure Criterion of Ionic Conductivity of Sr- and Mg-doped LaGaO_3 Ceramics

The valence electron structures of Sr- and Mg-doped LaGaO3 ceramics with different compositions were calculated by Empirical Electron Theory of Solids and Molecules （EET）. A criterion for the ionic conductivity was proposed, i.e. the 1/（nAnB） increases with increasing the ionic conductivity when x or y〈20% （in molar fraction）.

Analysis of Valence Electron Structure of RE in Solid Solution in Medium and Low Carbon Steel

According to EET theory, the valence electron structures of RE in the solid solution of austenite, pearlite and martensite were calculated. The influence of RE in solid solution on phase transformation of pearlite and recrystallization of martensite was explained by the valence electron structure data of phases. Calculating results indicate that C element is favorite to enhance the number of RE in the solid solution. RE in the solute solution shortens the incubation period of proeutectoid ferrite, increases its quantity and carbon content, decreases the quantity of pearlite and thickness of its lamellas and lamellar spacing, then the strength and hardness of pearlite are improved and granular pearlite can be obtained. RE dissolved in martensite intensifies martensite, enhances tempering stability of martensite, increases its recrystallization temperature and prolongs the holding time needed during tempering.

Study Segregation of Alloying Elements in Continuous Casting Slab with Valence Electron Structure

By calculating the electron structures of the phases that phosphor, sulfur and alloying elements dissolving inγ-Fe, the reason why alloying elements can bring centerline segregation in continuous casting slab (CCS) with nA, the number of electrons on the strongest covalent bonds, and the structure formation factor S were investigated, and an electron structural criterion to control and to eliminate the centerline segregation was advanced. Basing on this, the electron structures of a part of rare earth phosphides and sulfides are calculated, the physical mechanism that rare earth elements can control the segregation of phosphor and sulfur is analyzed, and the criterion is well verified.

CALCULATION OF VALENCE ELECTRON STRUCTURE IN L_2~'-TYPE COMPLEX SOLID SOLUTIONS

Based on the empirical electron theory of solids and molecules of S. H. Yu, this paper proposes (i) the calculating model of valence electron structures in L_2~'-type substitutional and interstitial complex solid solutions; (ii) the bond length difference analysis (BLD) method of unknown bond length structure solid solutions; (iii) the treatment of uncertainty of BLD analysis solution.

Tuning the electron structure enables the NiZn alloy for CO_(2) electroreduction to formate

Formate is an important liquid chemical,which can be produced by electrocatalytic carbon dioxide reduction reaction(CO_(2) RR).Most of the metal catalysts for CO_(2) RR to formate are toxic or noble metals,such as Cd,Hg,Pb and Pd,leading to the environmental pollution or increased production costs.Herein,we develop an environmentally friendly and low-cost NiZn alloy catalyst for CO_(2) RR to formate.The X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM) confirm the alloy structure of the prepared NiZn catalyst. As for a catalyst for CO_(2) RR,the NiZn alloy exhibits the FE_(HCOO)^(-)(Faraday efficiency of HCOO^(-)) of 36±0.7% at-0.9 V vs.RHE in 0.1 M KHCO_(3), and remarkable stability for 40,000 s at-0.8,-0.9,-1.0 and-1.1 V vs.RHE,respectively.Theoretical calculation results indicate that the NiZn alloy exhibits the middle valence electron structure between the Zn and Ni metal,resulting in the favorable pathway for HCOOH formation but unfavorable for the hydrogen evolution reaction and CO production.The Ultraviolet Photoelectron Spectroscopy results verify the modulated valence electron structure for NiZn alloy as compared to Ni and Zn,consistent with the theoretical calculation results.This work provides new insights into design of alloy catalysts for CO_(2) RR to formate.

Calculations of stability of alloyed cementite from valance electron structure

Based on the empirical electronic theory of solids and molecules （EET）, the actual model for unit cell of cementite （0-FeaC） was built and the valence electron structures （VES） of cementite with specified site and a number of Fe atoms substituted by alloying atoms of M （ M=Cr, V, W, Mo, Mn ） were computed by statistical method. By defining P as the stability factor, the stability of alloyed cementite with different numbers and sites of Fe atoms substituted by M was calculated. Calculation results show that the density of lattice electrons, the symmetry of distribution of covalent electron pairs and bond energy have huge influence on the stability of alloyed cementite. It is more stable as M substitutes for FeE than for Fe1. The alloyed cementite is the most stable when Cr, Mo, W and V substitute for 2 atoms of Fe2 at the sites of Nos. 2 and 3 （or No. 6 and No. 7）. The stability of alloyed cementite decreases gradually as being substitutional doped by W, Cr, V, Mo and Mn.

Electron theory study on the effect of Mn on as-cast structure of Fe-C-Cr-Mn cast irons

The valence electron structure of alloying austenite of 3C-15Cr high chromium white cast iron with different Mn contents from 1% to 6% is analyzed by BLD method and EET. Results show that the addition of Mn has major influence on the valence electron structure of the alloying austenite, especially on that of Fe-C, Fe-C-Cr and Fe-C-Cr-Mn unit cells of it. The effect becomes weak when Mn content is over 4%. Based on the effect of n~, F~~, the weighting of each unit cell and the degree of undercooling on phase transition of the aus- tenite, we can calculate the retained austenite content of as-cast structure of the high chromium white cast iron. The calculation results coincide well with those of the experiment. The phase transition characters of the austenite in high chromium white cast iron can be forecasted through valence electron structure analysis of alloying austenite by BLD method and EET on the basis of Fe-C-Cr equilibrium phase diagram.

Correlation between electronic structure and energy band in Eu-doped CuInTe_2 semiconductor compound with chalcopyrite structure

The Eu-doped Cu（In, Eu）Te2 semiconductors with chalcopyrite structures are promising materials for their applications in the absorption layer for thin-film solar cells due to their wider band-gaps and better optical properties than those of CuInTe2. In this paper, the Eu-doped CuInTe2 （CuIn1-xEuxTe2, x = 0, 0.1, 0.2, 0.3） are studied systemically based on the empirical electron theory （EET）. The studies cover crystal structures, bonding regularities, cohesive energies, energy levels, and valence electron structures. The theoretical values fit the experimental results very well. The physical mechanism of a broadened band-gap induced by Eu doping into CuInTe2 is the transitions between different hybridization energy levels induced by electron hopping between s and d orbitals and the transformations from the lattice electrons to valence electrons for Cu and In ions. The research results reveal that the photovoltaic effect induces the increase of lattice electrons of In and causes the electric resistivity to decrease. The Eu doping into CuInTe2 mainly influences the transition between different hybridization energy levels for Cu atoms, which shows that the 3d electron numbers of Cu atoms change before and after Eu doping. In single phase CuIn1-xEuxTe2, the number of valence electrons changes regularly with increasing Eu content, and the calculated band gap Eg also increases, which implies that the optical properties of Eu-doped CuIn1-xEuxTe2 are improved.

Differences of grain-refining effect of Sc and Ti additions in aluminum by empirical electron theory analysis

The differences of grain-refining effect between Sc and Ti additions in aluminum,which cannot be substantially explained by traditional theories,were carefully studied.The empirical electron theory(EET) of solids and molecules was employed to calculate the valence electron structures(VES) of Al3Ti and Al3Sc.The conclusions can be drawn that,in the two alloys Al-Ti and Al-Sc,the different valence electron structures of Al3Ti and Al3Sc and the consequent differences of growth habit of the two particles,and the different interfacial electron density between particles and matrix fundamentally lead to the differences of grain-refining effect between Sc and Ti additions on aluminum and make Sr the better grain-refiner of aluminum.

Valence electronic structure of tantalum carbide and nitride

The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent,metallic and ionic characters. For a quantitative analysis of the relative strength of these components,their ionicities have been calculated by implanting the results of EET to the PVL model. It has been found that the ionicity of tantalum carbide is smaller than that of tantalum nitride. The EET results also reveal that the covalent electronic number of the strongest bond in the former is larger than that of the latter. All these suggest that the covalent bond of TaC is stronger than that of TaN,which coincides to that de-duced from the first-principles method.

DETERMINATION AND APPLICATION OF LARSON-MILLER PARAMETER FOR HEAT RESISTANT STEEL 12CrlMoV AND 15CrMo

Based on the analysis and processing on relative empirical formula and data, C-values in Larson-Miller (P) expression, P= T(C + Igt), have determined for pearlitic heat resistant steel 12Cr1MoV and 15CrMo(20.62 and 20.30). The simulation experiments of high temperature aging, heated from 1.5 to 873 hours, have been designed and performed for its verification. And in combination with published information and the present nearly quantitative works, it has further been verified that both the degradations of microstructures and mechanical properties show a good accuracy and practicability using the Larson-Miller parameter with the present determined C-values. Finally, the effects of carbon content on C-value are analyzed by the empirical electron theory of solids and molecules (EET).

EFFECT OF HETEROGENEOUS DISTRIBUTION OF C AND ALLOYING ELEMENTS ONγ/α′TRANSFORMATION IN A Fe-Mn-Cr-C ALLOY

The heterogeneous distribution of C and metallic alloying elements as well as the phase com- position changes before and after cold deformation of an Fe-Mn-Cr-C alloy have been stu- died by the use of Mssbauer spectroscopy.The austenites without and with C and metallic alloying elements are found in the alloy in as-solid solution state.While the martensites with- out and with C and alloying elements may be induced by cold deformation.The transforma- tion from austenite to martensite in the alloy is confirmed via theoretical computation and ex- periments to be controlled by the number of covalent electron pairs forming covalent bond in austenitic crystal cell of the alloy.The formation of strong covalent bond between C and me- tallic elements can vigorously retard the γ/α' transformation.

THE CALCULATION OF THE COHESIVE ENERGY OFГPHASE IN THE TRANSITIONAL LAYER FE ZN OF HEAT GALVANIZED SHEET USED IN CARS

hethesisanalysesthevalenceelectronstructuresof phase Γin Fe Zn transitionallayerof heat galvanized sheet used in cars by applying the Empirical Electron Theory of Solids andMolecules, and calculatesthebond energy ofthe major bondsand cohesiveenergy ofcrystals,from which we draw theconclusion:sincecrystal has alargercohesiveenergy, it has higherhardness, butsinceitsbondenergyisratherlow ,itiseasytobreak under pressurefrom out side, and thecrackiseasytocome up andspreadin phase Γ.

Effect of cerium on structure,magnetism and magnetostriction of Fe_(81)Ga_(19) alloy

FeGa alloy is a new kind of magnetostrictive material, and rare-earth cerium can improve its magnetostrictive property.（Fe（81）Ga（19））（100-x）Cex（x = 0, 0.3 at%, 0.7 at%, 1 at%） samples were prepared by doping cerium in Fe（81）Ga（19） alloy. Their microstructures and phases were studied, and valence electronic structures were investigated. Electromagnetic parameters, such as coercivity, saturation magnetization,remnant magnetization and saturation magnetostrictive coefficients（λs） of every sample were measured.Cerium atoms are distributed at grain boundaries, and the Ce-doped alloys remain the A2 structure of FeGa alloy. When x is 0.7, the value of saturation magnetism is 217.08 emu/g, which is the maximum in the Ce-doped samples. The equivalent half length of single bond is the maximum also, and reaches to0.11380 nm. At the same time, the number of covalent electrons is 3.5672, and is the minimum of the Cedoped samples. Its As is the largest in the four samples. The change of As results in the change of equivalent half length of single bond in Ce-doped alloy.