Spacings between Similar Features, Such as Step Heights

Spacings between Similar Features, Such as Step Heights 

The techniques of surface science, originally developed largely through the investigation of single-element crystalline materials, have since been applied to many multicomponent systems. Of these, surface alloys and alloy surfaces form a significant subset. Both topics are covered in separate articles in this volume. Of aU known alloys or intermetalhc compounds, QCs have been among the most 

A QC (a quasiperiodic crystal) is a form of soHd matter that exhibits order without periodicity. QCs are often associated with classically forbidden rotational symmetries, although strictly speaking, this is not a necessary feature [1]. In this chapter, we are concerned with QCs composed of metal atoms, although quasiperiodicity has also been discovered in block copolymers [4], Hquid crystals [5], and nanoparticle superlattices [6]. Many excellent reviews and books are available that provide an introduction to aU aspects of QCs [7-12]. 

The majority of known metallic QCs have one of two types of structures icosahedral and decagonal. In icosahedral materials, the highest symmetry axis is fivefold. The icosahedral (i-)QCs can essentially be considered quasiperiodic in three dimensions. In decagonal materials, the highest symmetry axis is 10-fold. 

The decagonal (d-) QCs consist of 10-fold quasiperiodic planes that are stacked periodically along the 10-fold axis. The surfaces of QCs discussed in this chapter aU have icosahedral or decagonal stracture. 

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