What is Physics The Physics Site Navigator above requires JavaScript. Please enable it or navigate using this table. The Topics Navigator requires JavaScript 1.1 or higher. Please enable it or navigate using the Home page. It is often simpler to find the flux through one surface of an object than through another.
Any solid object is a crystal.
The total energy of a crystal can be calculated at any point of the solid. The total energy in a point inside the crystal is the result of contributions of all atoms surrounding that point. The total energy in a point at the surface of the crystal is only the result of contributions of atoms belonging to the crystal. There are no such atoms outside the surface of the crystal. Therefore, the total energy at the surface is less than the total energy inside the crystal.