On the spectral frequency distribution of translational vibrations in a face-centered cubic lattice of the C60 fullerite

The spectral frequency distribution g(ω) of translational lattice vibrations in the face-centered cubic phase of the C₆₀ fullerite at T = 300 K is calculated by the superposition method. The contribution from the translational vibrations to the heat capacity C _V of the C₆₀ fullerite and the x-ray characteristic temperature gJ_R entering into the exponent of the Debye-Waller factor are determined using the calculated frequency distribution g(ω). The results of the calculations are in good agreement with experimental data. It is noted that the librational and intramolecular lattice vibrations observed in the C₆₀ fullerite do not contribute significantly to the temperature-induced decrease in the x-ray diffraction intensity at T = 300 K. The Grüneisen parameters γ_mod calculated from the x-ray diffraction data are consistent with the thermodynamic Grüneisen parameters γ_lat at temperatures T ≤ 80 K but substantially exceed those at T ≈ 300 K. New x-ray diffraction experiments are proposed for independently determining the anomalously large negative values of the parameter γ₀, which is actually an orientational analog of the Grüneisen parameter.     

Electrostatic response and surface electron states of a Ca(001) face-centered cubic film

The electron response of a Ca(001) face-centered cubic film to an external electrostatic field is calculated. The results of calculations are compared with the previously obtained data on the electron response of a Cu(001) film. The energy location of occupied and unoccupied excited surface states of the Ca(001) film is determined.     

Migration of vacancies and impurities on the (111) surface of a face-centered cubic lattice

The paper presents an analytic study of impurity atom movements over the (111) surface of a face-centered cubic lattice initiated by the diffusion of vacancies. If multiple collisions of a single impurity with vacancies are taken into account, impurity movement acquires the character of Brownian movement. At long times, the time dependence of the mean-square displacement of the impurity insignificantly differs from linear, and its spatial distribution is close to normal, which allows us to introduce a diffusion coefficient. An analytic equation obtained for this diffusion coefficient differs from the product of the diffusion coefficient of vacancies by their relative concentration by a numerical factor only.     

C60 adsorption on Cu(110) studied by optical spectroscopy

The formation of the interface between C₆₀ thin films and the Cu(110) surface has been investigated in situ using reflectance difference spectroscopy (RDS). The electronic interaction between C₆₀ molecules in the first monolayer and the substrate inhibits low‐energy intramolecular transitions, whereas the C₆₀ molecules above the first monolayer are effectively decoupled from the substrate. The morphology of C₆₀ thin films prepared at room temperature is thermally stable up to 500 K. Above this threshold, optical spectroscopy and low energy electron diffraction (LEED) indicate the formation of rather large three dimensional C₆₀ islands on a one monolayer thick wetting layer. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Strain hardening of alloys with face-centered cubic lattice

A brief review is given of the peculiarities of the strain hardening of face-centered cubic (fee) alloys as compared with pure metals. The fundamental equations connecting the strain hardening characteristics to the quantitative characteristics of the dislocation structure and the slip trace picture are considered in application to alloys with a high friction stress of a nondislocation nature _F. The shape of the strain hardening curves of alloy mono- and polycrystals is analyzed; it is shown that it depends substantially on the stress level F.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 132–150, August, 1976.     

Theoretical prediction of ferrimagnetism in face-centered cubic iron

The magnetic structure of fcc Fe has been investigated in a range of lattice constants from a = 3.50 to 3.75 Å by the first-principles all-electron linearized augmented plane wave method in the local spin-density functional approximation. Besides the previously reported antiferromagnetic phase, one high-spin and two low-spin ferromagnetic phases, a ferrimagnetic phase is predicted to coexist in the range of a = 3.59 to 3.67 Å.     

Thermal-induced change in surface termination of DyScO3(110)

Auger electron spectroscopy using excitation by grazing impact of protons and by impact of electrons was applied to determine the elemental composition of the topmost and near-surface layers of DyScO₃(110). The vicinal DyScO₃ crystals were annealed at 1320 K in O₂ and Ar atmospheres by varying annealing time. The prepared surfaces show regularly arranged, smooth terraces with single-atomic steps. The surfaces have DyO termination after annealing in oxygen flow for 30–60 min. Annealing for 600 min of DyScO₃ in oxidizing or inert atmospheres resulted in a ScO_x termination.     

Vibrational properties of the adsorbed monolayer on face-centered cubic crystals

Calculations of mean-square displacements 〈u²〉 of the atoms in adsorbed monolayers on fcc crystals are presented and compared with LEED experimental results. This text is restricted to the case of a C(2 × 2) adsorbed layer on a (100) surface [experimental case of Ni(100) with adsorbed sulfur, sodium, cesium or oxygen]. 〈u²〉's perpendicular to and parallel to a (100) surface are calculated for the adsorbed atoms and the atoms of the first surface layer of the crystal. The values obtained are compared with those for a clean (100) surface and the volume of the crystal. Every possibility for force constants between adsorbate and substrate atoms is examined. It is shown that the measurement of 〈u²〉 perpendicular to the (100) surface yields the adsorbate-substrate force constants and that 〈u²〉 parallel to the (100) surface yields the adsorbate-adsorbate force constants.     

Monte Carlo study of entropy for face-centered cubic Ising antiferromagnets

A face-centered cubic Ising model with nearest neighbor antiferromagnetic exchangeJ _nn in the presence of a magnetic fieldH is investigated by Monte Carlo methods. Free energy and entropy of the model are obtained by integrating the equation of state along various paths, starting at suitable reference states. It is shown that at low temperatures first-order phase transitions can be located with very good precision. At the two critical fieldsH _c1/|J _nn |=4,H _c2/|J _nn |=12 a residual ground-state entropyS(0) is found, which is estimated as aboutS(0)/k _B (ln 2)/3 in both cases.In the presence of a ferromagnetic next-nearest neighbor exchange there is no longer a nonzero entropy at the critical fields, however. ForR+J _nnn /J _nn +–1 we find the same structure of the phase diagram as qualitatively predicted by Domany et al., where lines of 3-state and 4-state Potts model-like transitions meet at a multicritical point atH=0. Some consequences of our results for interpreting the ordering of face-centered cubic binary alloys are also discussed.     

Thickness dependence of the anomalous Hall effect in disordered face-centered cubic FePt alloy filmsThickness dependence of the anomalous Hall effect in disordered face-centered cubic FePt alloy filmsThickness dependence of the anomalous Hall effect in disordered face-centered cubic FePt alloy films

The anomalous Hall effect in disordered face-centered cubic （fcc） FePt alloy films is experimentally studied. The longitudinal resistivity independent term of the anomalous Hall conductivity （AHC） increases and approaches saturation with increasing film thickness. The contribution of side jump scattering is suggested to decrease monotonically with increasing film thickness, which can be ascribed to the variation of the surface scattering with the film thickness. The sign of the skew scattering contribution to the AHC is opposite to that of the intrinsic contribution in the system.     

Study of C60/Au(110)-p(6x5) reconstruction from In-plane X-Ray diffraction data

Fullerene molecules absorbed on the highly anisotropic Au(110)-p(1x2) surface induce an ordered p(6x5) superstructure that has been solved by applying the 2D "direct methods" difference sum function to the surface x-ray diffraction data set. We found that the C (60)-gold interface is structurally much more complex than the one previously suggested by scanning tunneling microscopy data [J. K. Gimzewski, S. Modesti, and R. R. Schlittler, Phys. Rev. Lett. 72, 1036 (1994)]. Indeed a large fraction of Au surface atoms are displaced from their original positions producing microscopic pits that may accommodate the fullerene molecules.     

Strengthening effect of short-range order esf ternary face-centered cubic substitutional solutions

The increase produced by short-range order in the resistance to the movement of dislocations _sro in ternary f. c. c. substitutional solid solutions was studied. A general expression for _sro was derived taking into account the correlation on the first three coordination spheres and the change in the entropy associated with the passage of dislocations. The expressions obtained were used for qualitative calculation of the concentration dependence of _sro for several ternary systems.     

Change in the lattice properties and melting temperature of a face-centered cubic iron under compression

All four parameters of the Mie–Lennard-Jones pair interatomic potential have been determined, and the state equation (P) and baric dependences of the lattice properties of an fcc iron are calculated using a previously proposed method. The dependences have been studied for the following properties: Debye temperature; the first, second, and third Gruneisen parameters; isothermal bulk modulus B _T and B′(P); isochoric specific heat C _v and C _v ′(P); isobaric specific heat C _p ; coefficient of thermal expansion α _p and α _p ′(P); specific surface energy σ and σ′(P). Calculations performed along two isotherms (1500 and 3000 K) have shown good agreement with the experimental data. Analytical approximations of the baric dependences for B′(P), α _p (P), C _p (P), and σ′(P) have been obtained, and it is shown that at P → ∞ the functions B _T (P) and σ(P) change linearly, while the functions α _p′(P) and C _p ′(P) tend to zero. The calculated baric dependence of the melting temperature shows good agreement with the experimental data.     

Photonic dispersions of semiconductor-quantum-dot-array-based photonic crystals in primitive and face-centered cubic lattices

We study the energy dispersions of photonic crystals based on the semiconductor-quantum-dot arrays. It has been shown that for the most commonly used semiconductor materials, and as compared with the primitive cubic lattice, the photonic crystal in a face-centered cubic (fcc) lattice exhibits a very promising energy dispersion relationship with an overall photonic bandgap. The bandgap is most prominent along the Λ(Γ–L) line inq space. The results explain the difficulties in fabricating photonic crystals in fcc lattices. They explain also the experimental works of Vlasov et al. [Physical Review B55, R13357–13360 (1997)], where it has been demonstrated that for CdS nanocrystals embedded in fcc porous silica matrices the photonic bandgaps are observed for any direction of the radiation incidence, being most pronounced for the [111] direction.