  In this paper, we study chain melting state in the commensurate host-guest
structure of calcium. We trained a NN (neural network) force field with
DeepMD-kit, and by implementing classical simulations, we found that the
convergence of z-proejcted MSD of guest atoms needs at least 8192-atom
supercell. We ascribe the origination of chain melting to the phase transition
at 600 K, in which the arrangement of guest chains transform from a
checkerboard pattern to a stripe pattern, and the energy barrier of sliding
chains against each other is obviously reduced. We also found that the chain
melting state of calcium could be separated into two 2D (two-dimensional) and
3D (three-dimensional) disorder, with distinct chain dynamics.
