system
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human
Why metals are crystalline and not amorphous?

Gibbs free energy equation : G = H - TS,
H: Enthalpy
T: absolute temperature
S: Entropy,
Since an amorphous structure has more entropy than a crystalline structure, which should reduce the Gibbs free energy, so why most solids exist in a crystalline state and not amorphous ?
gpt
Better, dG = dH - TdS. Now, for the TdS term to be dominating, it needs to be larger than dH. In crystallization, entropy is lost and dS is negative, so -TdS is positive. Meanwhile, dH is always negative for crystallization: the system releases energy when the atoms are locked into the right place, because it's energetically better than a less optimal orientation. So, dH and -TdS work in opposite directions. dG can be negative - i.e. the reaction is spontaneous - if -dH is bigger than -TdS, i.e the enthalpy trumps the entropy gain.

When we have a situation where enthalpy differences are very small, in this case indeed it happens so that entropy dominates, and fractal or amorphous shapes are produced.