Crystalline order is the simplest ordering that atoms could possibly be arranged ti for a solid, but why are the low energy arrangements of atoms so often in a periodic way ? it is not really easy to answer for first principles.
Thank you, but i have this doubt because when we see gamma iron and alpha iron one is magnetic and other is not. Some times during the course of time because of variations in pressure and temperature some crystal structures may change. How to explain these changes?