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1.
本文将元素变量(φ*和nWS)和MAEAM相结合,从原子尺度上对10种fcc金属Cu,Ag,Au,Ni,Pd,Pt,Rh,Al,Ir和Pb的38个不同晶面的表面能进行模拟计算及各向异性分析. 结果表明,fcc金属的密排面(111)的表面能最小,则该晶粒取向优先生长,与实验结果和第一原理的LMTO-ASA计算结果一致;各个晶面的表面能均随着其他晶面与(111)晶面的夹角cosθ(hkl)的增长而呈线性
关键词:
FCC金属
MAEAM
表面能
表面偏析 相似文献
2.
B. Luk'yanchuk N. Bityurin S. Anisimov D. Bäuerle 《Applied Physics A: Materials Science & Processing》1993,57(5):449-455
The stability of a planar surface upon pulsed UV-laser irradiation is studied with special emphasis on polymer ablation. Here, we consider a two-level system in which the excitation energy is dissipated via stimulated emission, non-radiative transitions, and activated desorption of excited species. With thermal relaxation times t
T10–10 s the ablation front turns out to become stable. This could explain the smooth surfaces obtained after pulsed UV-laser ablation of pure and stress free organic polymers. The situation is quite different for materials, for example metals, where fast thermal relaxation of the excitation energy within times, typically, t
T<10–11 s, gives rise to instabilities which result in surface roughening.On leave from the Institute of General Physics, Russian Academy of Sciences, 117942 Moscow, RussiaOn leave from the Institute of Applied Physics, Russian Academy of Sciences, 603600 Nishnii Novgorod, Russia 相似文献
3.
The surface segregation energies for a single metal impurity to the (100) surface of nine fcc metals (Cu, Ag, Au, Ni, Pd,
Pt, Rh, Al and Ir) have been calculated using the MAEAM and molecular dynamics (MD) simulation. The results show that the
effect of the surface is down to the fourth-layer and an oscillatory or monotonic damping (|E
1| > |E
2| > |E
3| > |E
4|) phenomenon in segregation energy has been obtained. The absolute value of the segregation energy E
1 for a single impurity in the first atomic layer is much higher than that in the nether layers. Thus, whether the surface
segregation will work or not is mainly determined by E
1 which is in good relation to the differences in surface energy between the impurity and host crystals ΔQ = Q
imp − Q
hos. So we conclude that an impurity with lower surface energy will segregate to the surface of the host with higher surface
energy.
相似文献
4.
L.L. Hirst 《物理学进展》2013,62(93):759-782
The application to the E.P.R. behaviour of dilute alloys of the generalized s-d interaction model appropriate to a 3d impurity with orbital degrees of freedom is considered. It gives rise in some cases to a large spin-lattice relaxation rate in addition to the usual cross relaxation to the conduction-electron spin. Our calculation shows why bottlenecking is effective for some 3d impurities and ineffective for others, leading to qualitative differences in the observed E.P.R. behaviour. It is emphasized that, as a result of the bottlenecking phenomenon, E.P.R. is a uniquely powerful method for determining the electronic states of 3d impurities in metals. 相似文献
5.
6.
The magnetic properties of very thin ferromagnetic Fe films (1–10 atomic layers) in contact with nonmagnetic amorphous metals are investigated. Apart from the demagnetization energy, which supports a magnetization in the plane of the film, an energy of magnetic anisotropy occurs in the interlayer, which has the tendency to orient the magnetization perpendicular to the surface. The anomalous Hall effect of the ferromagnetic films is used to investigate their magnetic properties. From the measurements, we get the applied magnetic field Bs, which is necessary to orient the magnetization perpendicular to the film surface. In addition to a constant term, Bs is proportional to 1/d, which is typical of surface effects and yields the energy of the interface anisotropy. The value of this energy is strongly dependent on the nonmagnetic metal and is smaller for the system Pb/Fe than for Sn/Fe. Furthermore, the experimental results show no drastic reduction of the atomic magnetic moment in the surface layer. 相似文献
7.
R.I. Eglitis 《Phase Transitions》2013,86(11):1115-1120
8.
Like liquid alkali metalsd-shell liquid metals show scaling behaviour in structure and interaction potentials. A realistic interaction potential model,
properly parametrized can reasonably describe the universality in the isothermal compressibility and vacancy formation energy
of 3d-liquid metals in electron ion plasma model. 相似文献
9.
A theoretical investigation was carried out on multilayer relaxation, surface energy and surface stress in [001] oriented rectangular f.c.c metal nanowires using the modified embedded atom method. Surprisingly, the multilayer relaxation behavior depends on the wire sizes in absolutely distinct trends for inward-relaxation metals Ag, Cu, and for outward-relaxation metals Ir and Ni. Specifically, the outmost interlayer relaxation increases with decreasing cross-section areas for Ag, Cu nanowires, while it decreases for Ir, Ni nanowires. This is due to the additional effect of surface stress, which, with the surface energy, increases with decreasing wire width monotonically. 相似文献
10.
《Surface science》1986,172(2):319-336
A combined experimental and theoretical study of multilayer relaxation at the Pb(110) surface is presented. Ion shadowing and blocking measurements show that the distance d12 between the outermost two atomic layers is smaller than the bulk interlayer distance d by as much as Δd12/d=−15.8±2.5%. For the relaxations of the second and third interlayer distances we find that they satisfy the empirical relation Δd23/d+0.75Δd34/d=+0.5±2.5%. Thermal vibration amplitudes are strongly enhanced at the surface. Our theoretical model, based on energy minimization of the total energy of a semi-infinite simple metal crystal, predicts oscillatory multilayer relaxation with Δd12/d=−15.9%, Δd23/d=+7.9%, Δd34/d=−6.8% and Δd45/d=+0.7%, in agreement with experiment. 相似文献
11.
Although during the last years one has seen a number of systematic studies of the surface energies of metals, the aim and the scientific meaning of this research is to establish a simple and a straightforward theoretical model to calculate accurately the mechanical and the thermodynamic properties of metal surfaces due to their important application in materials processes and in the understanding of a wide range of surface phenomena. Through extensive theoretical calculations of the surface tension of most of the liquid metals, we found that the fraction of broken bonds in liquid metals (f) is constant which is equal to 0.287. Using our estimated f value, the surface tension (γm), surface energy (γSV), surface excess entropy (−dγ/dT), surface excess enthalpy (Hs), coefficient of thermal expansion (αm and αb), sound velocity (cm) and its temperature coefficient (−dc/dT) have been calculated for more than sixty metals. The results of the calculated quantities agree well with available experimental data. 相似文献
12.
《Surface science》1993,297(1):L48-L54
We have Investigated the interplanar relaxation of the clean (0001)-(1 × 1) surface of magnesium at 100 K using a dynamical LEED I-V analysis. In contrast to almost all other metal surfaces, an expansion has been observed for the first interlayer spacing of this clean surface. Using an extended database, the results indicate that the first three interlayer spacings are relaxed from the bulk value by Δd12 = +1.9 ± 0.3%, Δd23 = +0.8 ± 0.4%, and Δd34 = −0.4 ± 0.5%. A comparison of this observed multi relaxation with experimental and theoretical results for similar free-electron closepacked metal surfaces, e.g. Al(111), suggests that a surface expansion is a normal property of high electron density simple metals. 相似文献
13.
V. D. Borman M. A. Pushkin V. N. Tronin V. I. Troyan 《Journal of Experimental and Theoretical Physics》2010,110(6):1005-1025
The electronic properties of nanoclusters of transition (Ni, Co, Cr) and noble (Au, Cu) metals deposited on the surface of
highly oriented pyrolytic graphite (HOPG) are studied using the method of X-ray photoelectron spectroscopy. The laws of variation
of a change ΔE
b in the binding energies of core-level electrons in the initial (ΔE
i) and final (ΔE
f) states of atoms in nanoclusters, the intrinsic widths γ of photoelectron lines, and their singularity indices α as functions
of the metal cluster size d are determined. A qualitative difference in behavior of the ΔE
i(d) and α(d) values in metals of the two groups (Ni, Cr versus Co, Cu) is found. The values of the final-state energy (ΔE
f < 0) and the line width (Δγ > 0) in the clusters of all metals studied vary in a similar manner. It is shown that a significant
contribution to E
i is due to a transfer of the valence-shell electrons at the cluster-substrate interface, which is caused by the contact potential
difference. The value of an uncompensated charge per nanocluster is determined as a function of the cluster size and the number
of atoms in the cluster. The behavior of ΔE
f(d) is controlled by the Coulomb energy of a charged cluster and by a decrease in the efficiency of electron screening, which
is different in the metals studied. The broadening of photoelectron lines is determined by a spread of the cluster sizes and
by lower electron screening in the final Fermi system. An asymmetry of the core-level electron spectra of nanoclusters can
be explained using notions about the electron-hole pair excitation near the Fermi level. The effect of the structure of the
density of electron states in the d band of transition metals on the asymmetry of photoelectron lines is considered and it is concluded that this structure near
the Fermi level qualitatively changes with a decrease in the nanocluster size. The obtained results indicate that the behavior
of the electron subsystem of clusters of the d-metals in a size range of 2–10 nm under consideration is close to the behavior of a normal Fermi system. 相似文献
14.
This work describes a calculation of the formation energy and volume for a vacancy in transition metals. One uses a tight-binding scheme for the d band and a Born-Mayer type potential to account for the repulsive part of the energy at small distances. The results show that the relaxation energy is small in all cases, less than 0.1 eV. This seems to be coherent with the good agreement obtained for the theoretical and experimental values of the formation energy Efv of the vacancy, without including relaxation. The center of the transitional series is found to give a contraction (formation volume of order ?0.4 at. vol.) whereas the edges are found to produce dilatations. 相似文献
15.
E. R. Smith 《Journal of statistical physics》1989,55(1-2):127-139
Studies of the mean spherical model with Coulomb interactions are continued, by considering a system on ad-dimensional lattice which is periodic ind–1 dimensions and has a free surface in the remaining dimension. It is shown explicitly that correlations along the free surface decay asy
–d
ind dimensions and show that the surface properties of this model are those expected for a charged system in its plasma phase. 相似文献
16.
R. Weißmann R. Koschatzky W. Schnellhammer K. Müller 《Applied Physics A: Materials Science & Processing》1977,13(1):43-46
Auger electron spectra of the transition metals Cr, Mn, Fe, Co and Ni as well as their oxides have been investigated in the
energy range between 0–100 eV. In each case of the clean metal surface the observed spectrum consists essentially of one Auger
line identified asM
2,3
VV transition. After oxidation a line doublet is observed revealing two transitions instead of one. Additional new Auger peaks
appear in the low energy range between 0–30 eV. The “splitting” of the Auger line can be explained as resulting from aM
2,3
V
dVd and aM
2,3
V
pVp transition. The latter is characteristic for the compound and can in a simple way be interpreted as a cross transition. 相似文献
17.
The dynamical properties of Rydberg hydrogen atom near a metal surface are presented by using the methods of phase space analysis
and closed orbit theory. Transforming the coordinates of the Hamiltonian, we find that the phase space of the system is divided
into vibrational and rotational region. Both the Poincaré surface of section and the closed orbit theory verify the same conclusion
clearly. In this paper we choose the atomic principal quantum number asn=20. The dynamical character of the exited hydrogen atom depends sensitively on the atom-surface distanced. Whend is sufficiently large, the atom-surface potential can be expressed by the traditional van der Waals force and the system
is integrable. Whend becomes smaller, there exists a critical valued
c. Ford>d
c, the system is near-integrable and the motion is regular. While chaotic motion appears ford<d
c, and the system tends to be non-integrable. The trajectories become unstable and the electron might be captured onto the
metal surface. 相似文献
18.
19.
20.
J. A. Alonso 《Zeitschrift für Physik B Condensed Matter》1981,40(4):307-309
The surface dipole barrierD of transition and non transition metals is calculated from experimental policrystalline work functions and theoretical chemical potentials obtained by the Augmented Spherical Waves Method. An universal linear relation is discovered betweenD andn
b
non-d
, the non-d part of the electron density at the boundary of bulk atomic cells. This suggests that the surface dipole barrier is mostly due to the non-d electrons. 相似文献