The entropy of a perfect crystal at absolute zero is exactly equal to zero. At absolute zero the system must be in a state with the minimum possible energy, and the above statement of the third law holds true provided that the perfect crystal has only one minimum energy state. By the 3rd law, entropy is zero, at zero K. If we think about what the temperature is, it is a measure of internal, randomized energy in a material. Absolute zero is a point at which thermal motions stop entirely.