Find the critical radius ratio for triangular void

The cation/anion radius ratio for a triangular arrangement of anions in which the cation is in contact with the anions (but does not push them apart) as shown in the figure is

The cation/anion radius ratio for a triangular arrangement of anions in which the cation is in contact with the anions (but does not push them apart) as shown in the figure is

The limiting radius ratio for tetrahedral voids has the range:

Find out the ratio of maximum number of triangular voids and rectangular voids formed by nine atoms according to HCP and square close packing in 2D respectively

Limiting radius ratio|Calculation of limiting radius ratio for different voids

Find the radius of an equilateral triangular plate about its median. Side of triangular is l.

In HCP or CCP constituent particles occupy 74% of the available space. The remaining space (26%) in between the spheres remains unoccupied and is called interstitial voids or holes. Considering the close packing arrangement, each sphere in the second layer rests on the hollow space of the first layer, touching each other. The void created is called tetrahedral void. If R is the radius of the spheres in the close packed arrangement then, R (radius of tetrahedral void) = 0.225 R In a close packing arrangement, the interstitial void formed by the combination of two triangular voids of the first and second layer is called octahedral coid. Thus, double triangular void is surrounded by six spheres. The centre of these spheres on joining, forms octahedron. If R is the radius of the sphere. in a close packed arrangement then, R (radius of octahedral void = 0.414 R). If the anions (A) form hexagonal close packing and cations (C ) occupy only 2/3rd octahedral voids in it, then the general formula of the compound is