The triply periodic minimal surface of the three space groups can be approximated as: cos x n + cos y n + cos z n = 0, (1) (primitive) sin x n cos y n + sin y n cos z n + sin z n cos x n = 0, (2) (gyroid) sin x n sin y n sin z n + sin x n cos y n cos z n + cos x n sin y n cos z n + cos x n cos y n sin z n = 0, (3) (diamond)