Surface properties of 3d transition metals

Using the projector augmented wave method within density functional theory, we present a systematic study of the layer relaxation, surface energy and surface stress of 3d transition metals. Comparing the calculated trends for the surface energy and stress with those obtained for 4d and 5d metals we find that magnetism has a significant effect on the surface properties. Enhanced surface magnetic moments decrease the size of the surface relaxation, lower the surface energy and surface stress, leading to compressive stress in Cr and Mn.     

Features of hydrogen interaction in the Pd-based alloys with 3d transition metals

The effect of an alloying metal and its magnetic state on the hydrogen absorption energy has been investigated in the Pd-based alloys Pd₃Me with 3d transition metals (Me = Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) using calculations from first principles. The full-potential and linearly augmented plane wave (FP LAPW) method has been used in the local density approximation (LDA) for the exchange-correlation potential in the framework of the density functional theory (DFT). It has been found that the hydrogen solubility in an alloy increases if the centers of mass of s and d metal bands and s hydrogen band shift strongly toward the Fermi level. The changes in properties of hydrogen absorption as a function of its position in a crystal lattice structure and magnetic state of an alloy have been analyzed.     

Trends in hydrogen chemisorption on transition metals

A systematic study of H adsorption on the close-packed surfaces of the transition metals in the 3d and 4d series is presented. The effect of the TM d band on the chemisorption bond is investigated, by embedding a cluster of TM muffin tins at the surface of an effective jellium-like medium. It is found that the broad and incomplete H/jellium resonance is narrowed, shifted down and made to contain more electrons as a result of hybridization with the TM d states. These effects are larger in the case of the 4d metals, thus indicating a greater participation in the chemisorption bond of the d electrons for these metals than for the 3d metals. Calculation of one-electron energy differences on going from the H on jellium system to that of H on the TM cluster are presented. Trends for the one-electron energy differences are compared to trends in experimental chemisorption energy. H adsorption in the three-fold hollow site with no secondlayer TM atom below the H site is favoured for the hcp metals, while no discernible preference between the two hollow sites is recorded for the fcc metals, with the exception of Rh where the site with no second-layer TM atom below is preferred.     

Energy of intermetallide formation for 3d transition metals

By the method of a model electron-density functional, the energy of alloy formation in the systems Fe-Ti, Co-Ti, Ni-Ti is calculated as a function of the volume, concentration, and degree of long-range order. The energy benefit of the appearance of compounds FeTi, CoTi, NiTi in the CsCl structure is established. For the given compounds, the equilibrium volumes and the magnitude of charge transfer are calculated. An analysis of the ordering energy as a function of the concentration and degree of long-range order is performed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 47–51, May, 1982.     

Magnetic properties of nanoparticles of 3d metals

The influence of size effects on the coercive force, magnetization, and Curie temperature in nanoparticles of 3d metals is considered. It is shown that experimental results obtained during the last two decades provide new information on peculiar magnetic properties of these particles.     

X-ray absorption spectra: K-edges of 3d transition metals,L-edges of 3d and 4d metals,and M-edges of palladium

The X-ray absorption spectra of the 3d and 4d transition metals have been calculated within the single-particle approximation by a new linearized augmented plane wave method. The spectra, calculated with sharp atomic and band-structure single-particle levels, have been convoluted with a Lorentzian broadening function whose width is the sum of that of the core hole and the excited electrons. Plots are shown for (i) the K-edge fine structures up to at least 100 eV above the edge for Ca, Ti, Cr, Co, Cu, and Zn, (ii) the L_{2, 3} white lines for Ca, Ti, Cr, Co, and Cu, (iii) the L₃ white lines for Sr, Zr, Nb, Ru, Rh, and Pd, and (iv) the M_{2, 3} and M_4,5 spectrum of Pd. Systematic features which depend on the crystal structure and the placement of the Fermi level with conduction band are briefly discussed.     

Magnetic properties of 3d transition metal monolayers on metal substrates

We report results of systematic calculations for magnetic properties of 3d transition metal monolayers on Pd(001) and Ag(001). We find large similarities to interactions of magnetic 3d impurities in the bulk. Therefore the overlayer results are supplemented with results for 3d dimers in Cu, Ag, and Pd. Differences between the two classes of systems are utilized to reveal the interaction within the overlayers and between overlayers and substrates. In virtually all cases we find both ferromagnetic and antiferromagnetic solutions, showing large magnetic moments and similar densities of states. From the trend of the calculations we conclude that V, Cr, and Mn overlayers favor the antiferromagnetic c(2×2) structure, while Ti, Fe, Co, and Ni prefer the ferromagnetic one.     

A theoretical study of the structure and stability of borohydride on 3d transition metals

The adsorption of borohydride on 3d transition metals (Cr, Mn, Fe, Co, Ni and Cu) was studied using first principles calculations within spin-polarized density functional theory. Magnetic effect on the stability of borohydride is noted. Molecular adsorption is favorable on Co, Ni and Cu, which is characterized by the strong s–d_zz hybridization of the adsorbate-substrate states. Dissociated adsorption structure yielding one or two H adatom fragments on the surface is observed for Cr, Mn and Fe.     

Temperature-induced local magnetic moments (TILMM) in monosilicides of 3d transition metals

Features of the formation of temperature-induced local magnetic moments (TILMM) and their influence on the magnetic and thermophysical characteristics of iron, cobalt, and manganese monosilicides are investigated. The results obtained for magnetic susceptibility and specific heat measurements are discussed within the framework of spin-fluctuation theory. Temperature-concentration dependences are established for the TILMM absolute value for mutual solid solutions Fe_1–xCo_xSi and Fe_1–yMn_ySi. It is shown that for a number of the alloys studied the saturation of the TILMM absolute value does not occur, while the anomalous behavior of the polytherm of their physical properties is associated with features of the band structure.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 18–23, April, 1988.     

3d过渡金属在NiAl中的占位及对键合性质的影响

通过赝势平面波方法系统地研究了3d过渡金属元素在B2-NiAl中的占位以及对键合性质的影响.通过形成能得出Sc,Ti,V 和Zn元素优先取代NiAl中的Al位,而Cr,Mn,Fe,Co和Cu优先取代Ni位.通过分析晶格常数变化量、电荷聚居数、交叠聚居数以及价电荷密度分布, 讨论了晶格畸变和键合性质的变化.结果表明: 取代Al的Sc,Ti,V和Zn元素掺杂使NiAl中晶格发生畸变,这对NiAl键合性质的变化起着重要作用,这些掺杂元素与第一近邻Ni原子产生强烈的排斥作用,形成反键,同时它们之间发生较大的电荷转 关键词： NiAl金属间化合物 3d过渡金属 第一性原理 键合性质     

Metal-insulator transition in hydrogen and in expanded alkali metals

Two methods are considered for testing the stability of an electron gas to formation of bound states round a pair of protons. In the first, the screened potential for the two protons is set up as a superposition, which is appropriate in a very high density electron gas. The condition for bound state formation is then examined in the two-centre problem. The density thus obtained is in the right density range to accord with the experiment of Hawke et al. for producing cold metallic hydrogen.This has encouraged us to attempt a more ambitious calculation, namely the investigation of the Heitler-London energy of a model H₂ molecule with screened electron-nuclear and electron-electron interactions, the screening being again through appropriate introduction of the Thomas-Fermi screening radius. The merit of this second model is that the theory contains the Heitler-London value of the dissociation energy of the free H₂ molecule in the limit when the density of the electron gas tends to zero. This feature, the binding energy of the diatomic and its importance in distinguishing the metal-insulator transition in hydrogen from those expected to occur in expanded alkali metals is stressed. The second point we stress is that, in both the models discussed above, there is a close connection with the one-centre criterion for bound state formation. Though we have not carried out detailed two-centre calculations for expanded alkali metals, nevertheless some discussion is given of the one-centre bound state criterion in these metals.Some remarks are also made on the dielectric function of molecular crystals, in relation to the insulator-metal transition.     

Oxides of 3d transition metals as sources for electromagnetic and acoustic metamaterials

A brief review of studies performed by the authors to determine the conditions under which antiferromagnetic media display dynamic properties similar to those of certain types of electromagnetic and acoustic metamaterials is presented.     

Correlation effects in 3d transition metals: Presence of a two-hole core-satellite in cobalt

Photoemission spectra of the 2p-level have been recorded from evaporated films of the 3d transition metals vanadium, chromium and cobalt. Structures on the high binding energy side of the spectra are observed; cobalt shows a weak satellite structure that resembles the well-known shakeup satellite in the nickel core level spectrum, only less intense, whereas the core level spectra of V and Cr only show satellites due to collective electron excitations.     

Invar properties in the rare earth-3d transition metal alloys

The RCo₂ and R₂Fe₁₇ compounds (R = rare earth) exhibit Invar-like thermal expansion anomalies below their ordering temperatures. These spontaneous volume magnetostrictions are discussed by considering their magnetic properties. In RCo₂ compounds there is no intrisinc Co-moment is induced by the exchange and applied fields. The volume expansion anomaly is associated with the onset of the 3d magnetic moment. IN R₂Fe₁₇ compounds there is an intrisinc Fe- moment. Magnetic structures give evidence for positive and negative exchange interactions between Fe atoms which are strongly distance dependent. The thermal expansion anomaly is a result of this distance of the magnetic interactions.     

Theory of chemisorption of hydrogen on transition metals and their alloys

A theoretical discussion is given of the changes in the heat of chemisorption of a hydrogen atom upon alloying a group-VIII metal with a group-IB metal. The emphasis is on two concepts: the ensemble effect and the ligand effect. The ensemble effect ascribes the changes in the heat of chemisorption primarily to changes in the geometry of the adsorption complex, whereas the ligand effect also takes into account changes in bond strength due to a different intrinsic activity of the bonding metal atoms.     

Analysis of the liquid structure of 3d transition metals from the Wills-Harrison model

Calculations of the liquid structure of 3d transition metals from the effective pair interactions of Wills and Harrison are performed by using the optimized random phase approximation in order to point out the influence of thes-electron pseudopotential on the repulsive and attractive forces governing the liquid structure. Our results are compared to those obtained in the Weeks, Chandler Andersen approximation and in the thermodynamic variational method.