Ours is an essentially infinite universe
And in such a universe, it's almost certain that these entities have already arisen by chance. One may just have to look very hard to find them- I can imagine a cloud of these somewhere in interstellar or intergalactic space.
If they emit no energy, so as to not break the laws of thermodynamics*, how does one use them as a crystal? Currently crystals are used by energising them and allowing them to oscillate, but they do emit energy.
* The Laws Of Thermodynamics, to wit:
Law 1: You can't win, you can only break even.
Law 2: You can only break even at absolute zero.
Law 3: You can't reach absolute zero.
Law 0: You must play the game at all times.