Substances with different chemical composition but the same crystalline form. Compare with crystal . A solid that does not have a repeating, regular three-dimensional arrangement of atoms, molecules, or ions. The shape results from the arrangement of the substances atoms, ions, or molecules.
Most crystals contain defects that can strongly affect their optical and electrical properties.
Compare with amorphous . A solid that has a repeating, regular three-dimensional arrangement of atoms, molecules, or ions. The change in enthalpy when one mole of solid vaporizes to form one mole of gas. Enthalpies of sublimation are always positive because vaporization involves overcoming most of the intermolecular attractions in the sublimation. The temperature at which the vapor pressure of a liquid is equal to the vapor pressure of the corresponding solid form.