what are triangular voids where are they present?

Dear student,

It must be tetrahedral void....

Tetrahedral voids

In close packing arrangement, each sphere in the second layer rests on the hollow (triangular void) in three touching spheres in the first layer. The centres of theses four spheres are at the corners of a regular tetrahedral. The vacant space between these four touching spheres is called tetrahedral void. In a close packing, the number of tetrahedral void is double the number of spheres, so there are two tetrahedral voids for each sphere  

Radius of the tetrahedral void relative to the radius of the sphere is 0.225

i.e. r_void / r_sphere = 0.225

In a multi layered close packed structure , there is a tetrahedral hole above and below each atom hence there is twice as many tetrahedral holes as there are in close packed atoms

i know about tetrahedral voids see there are four kinds of voids :- triangular , tetrahedral,octahedral,cubic

triangular  .155 - .255pm

cubic .732-1pm

but i dont much know about them so give me some info if u have any