Glide plane, axial

Fig. 195. Possible arrangements of molecules in /3 gutta-percha. Note that for Pea the axial nomenclature is changed this is done to attain the conventional orientation of symmetry elements in this space-group. (One symmetry element in this arrangement is not shown there is a glide plane parallel to the paper, having translation o/2.) R = right,...

It turns out that three types of glide plane can be differentiated. In the first type, the translation is in the direction of a principal lattice vector, that is, it is given by one of the vectors a/2, b/2, or c/2. For each of these, the plane must be parallel to the plane defined by the translation direction and one of the other two principal directions. Thus, if we have a glide plane parallel to the plane of a and c, the glide component may be either a/2 or c/2. Planes of this type are called axial glide planes and are symbolized a, b> or c, according to the direction of the glide. 

The displacement by in the first row and fourth column comes from the mirror reflection in the plane at x = 1/4. The A in the second and third rows of the fourth column are the components of the diagonal glide. The location of the transformed point is that marked by a comma (,) and M>+. The MR of the operation (rry A 0 0)[xyz], when the axial glide plane lies at y=lA, is... 

The combination of reflection and translation gives a glide plane. If the gliding direction is parallel to the a axis, the symbol for the axial glide plane is a and the operation is reflection in the plane followed by translation parallel to the a axis by a/2 . Similar axial glide planes b and c have translation components of b/2 and c/2, respectively. 

Axial glide plane 1 /2 lattice vector along line in projection plane a, b, or c... 

Glide plane A glide plane involves reflection across a plane combined with a translation. For an axial glide plane, denoted a, b or c, the translational component is or f, respectively. For a c-glide plane, if the mirror plane is perpendicular... 

The symbols for plane groups, the Hermann-Mauguin symbol, have been the standard in crystallography. The first place indicates the type of lattice, p indicates primitive, and c indicates centered. The second place indicates the axial symmetry, which has only 5 possible vales, 1-, 2-, 3-, 4-, and 6-fold. For the rest, the letter m indicates a symmetry under a mirror reflection, and the letter g indicates a symmetry with respect to a glide line, that is, one-half of the unit vector translation followed by a mirror reflection. For example, the plane group pAmm means that the surface has fourfold symmetry as well as mirror reflection symmetries through both x and y axes. 

Glide Operation that is a product of a mirror and a translation that is a fraction of the lattice vector in the plane of the mirror. There are axial glides, double glides, diagonal glides, and diamond glides. 

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