92168.pdf

144 The solid-gas interface

Square a * b, y = 90°

a

Rectangular a * b, y == 90°

a

• •

* • •

Centred rectangular a •* b, y = 90°

a

Hexagonal a = b, y = 120° Oblique a # b, y # 90°

a

Figure 5.15 Classification of nets

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4 • • • •

to make a different choice of unit mesh in order to show the
symmetry of the system more clearly. For. example, the centred
rectangular net can, alternatively, be viewed as an oblique net, as the
primitive mesh illustrates; however, the choice of a centred rectangular
unit mesh (bottom right hand corner) illustrates the surface geometry
better.