Do crystals have stronger intermolecular forces than amorphous solids.
Are the properties of amorphous solids vs. crystals explained by their structures?
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asked Jun 19, 2015 at 18:01
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1$\begingroup$ I didn't edit, but note, it's rather intermolecular forces than bonds. $\endgroup$– M.A.R.Jun 19, 2015 at 18:02
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3$\begingroup$ The structure, of course, does lead to many of the properties. Now, for an example to ponder: amorphous silicon is a four-fold coordinated, tetrahedrally-bonded semiconductor, just like crystal silicon. Well, except that it has no long range order. It is also a separate thermodynamic phase exhibiting a first order phase transition to the solid. The band gap of the amorphous phase is similar to that of the crystal. The average bond length is similar. The phonon energies are similar. The average atomic forces are slightly in the crystal's favor, but it is the lowest free energy allotrope. $\endgroup$– Jon CusterJun 19, 2015 at 18:22
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2 Answers
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Diamond crystal has much stronger bonds than amorphous red phosphorus. Amorphous sodium/calcium silicate, known as glass, has much stronger bonds than crystalline metallic sodium. (Also, in all four cases the word intermolecular doesn't really apply, because these compounds are not made of molecules.)
You see that the answer depends primarily on the particular compound, rather than on its being crystalline or amorphous. In cases when something can be either crystalline or amorphous with the same chemical composition, the bonds in both are pretty much the same, as explained in the comment by Jon Custer.
Oh, and yes, chemical and physical properties of pretty much anything are explained by its structure.
answered Oct 12, 2015 at 7:35
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For some materials that can exist in the amorphous or crystaline state like quartz or corundum, the crystalline state is harder, that is, requires a harder substance to even begin to scratch it. For other other materials like diamond, the amorphous state is harder. However, for quartz and corundum, the amorphous state is less breakable than the crystalline state once they have already been scratched. That's because the cracks in the crystalline form introduced by scratching are less likely to loop around into a chip to when the crystal undergoes a collision with a hard surface, the tension is greatly magnified at the tip of the crack, which causes it to propagate and if the collision is fast enough, the crack will propagate through leading to fracture.
