SiのSurface melting, Cu3Auのorder disorder

Short-range ordering of Cu3Au above Tc in the topmost 80 A of a (001) face

M. Kimura, J. B. Cohen, S. Chandavarkar and K. Liang : Journal of Materials Research, Vol. 12, No. 1 (1997)  75-82

 

The short-range order in the near surface region of the Cu3Au(001) face was investigated above the critical temperature by glancing-incidence x-ray diffraction, measuring the diffuse intensity throughout a two-dimensional region of reciprocal space. This intensity was analyzed quantitatively to obtain the two-dimensional Cowley–Warren short-range-order parameters and atomic displacements. Monte-Carlo simulation based on these values has revealed that the atomic configurations in the surface consist of ordered domains and clusters in a disordered matrix. There is a large number of {10} antiphase domain boundaries (APDB).

 

 

Geometry of surface x-ray diffraction experiments. Shadowed planes are those involved in in-plane diffraction such as (100). The coordinates show the crystallographic orientation of the specimen.Fig.1 Geometry of surface x-ray diffraction experiments. Shadowed planes are those involved in in-plane diffraction such as (100). The coordinates show the crystallographic orientation of the specimen.

 

Contour map of the diffuse intensities in the two-dimensional reciprocal lattice hk.

Fig.2 Contour map of the diffuse intensities in the two-dimensional reciprocal lattice hk.

 

 

Part of the computer simulation of the structure of the Cu3Au(001) surface 56 K above the bulk Tc. Au and Cu atoms are represented by closed and open circles, respectively. One of the ordered domains and an Au cluster are indicated by the solid and the broken lines, respectively.

Fig.3 Part of the computer simulation of the structure of the Cu3Au(001) surface 56 K above the bulk Tc. Au and Cu atoms are represented by closed and open circles, respectively. One of the ordered domains and an Au cluster are indicated by the solid and the broken lines, respectively.

 

 

Relative interaction potentials, VlmyV11, in Cu3Au. (Interatomic distance is in units of 2rlmya0.) The fitted Friedel oscillation is shown as a full line.

Fig.4 Relative interaction potentials, Vlm/V11, in Cu3Au. (Interatomic distance is in units of 2rlm0.) The fitted Friedel oscillation is shown as a full line.

 

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