In this section, we will introduce how to convert the DFT labeled data into the data format used by DeePMD-kit.
The DeePMD-kit organize data in systems. Each system is composed by a number of frames. One may roughly view a frame as a snap short on an MD trajectory, but it does not necessary come from an MD simulation. A frame records the coordinates and types of atoms, cell vectors if the periodic boundary condition is assumed, energy, atomic forces and virial. It is noted that the frames in one system share the same number of atoms with the same type.