In many literature, it is explained in the high index facets surface atoms arrangements are quite different than low index facets which i couldn't understand .
You can also turn this question around and it might be easier to understand: Since low indexed planes are often closer packed they are more "stable" against any attack, i.e. during chemical reactions, solution etc. More stable means less reactive... Therefore, startiing from a sphere during solution experiments these planes become finally visible.
The higher indexed your single crystal surfaces are, the more steps and kinks etc you will encounter. However, usually chemical reactions first take place at those inhomogeneities, e.g. by an enhancement of the local electric fields (like in electron field emission), i.e. an electron transfer (=synonymous for a chemical reaction) may take place easier. There are several papers in the literature, that adsorption first takes place in step sites, and there is a diffusion barrier for diffusion across the steps. All those observation can in principle promote the reactivity of stepped (=highly indexed) surfaces! Hope this helps, Dirk
You can also turn this question around and it might be easier to understand: Since low indexed planes are often closer packed they are more "stable" against any attack, i.e. during chemical reactions, solution etc. More stable means less reactive... Therefore, startiing from a sphere during solution experiments these planes become finally visible.
The sentence "High index crystal facets are more reactive than low index crystal facets of same crystal" is generally true, but it is also a crude approximation, typical of crystallographers who didn't study the fundamental of equilibrium and crystal growth.
If you are interested to understand this basic problem you should study the Hartman-Perdok approach to the growth morphology of crystals. Don't hesitate to contact me about this topics. I'll send you a rich documentation.
@ Dino Aquilano: You are absolutely right. We are often using simplifications, rough approximations etc which do not work in general. The same is valid for Friedels's law which is actually Friedel's rule in order to better express the character of this statement. Therefore, many thanks that you pointed out this missing message in my comment.
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