The histograms of distance between surface atoms have been drawn. It's
found that in liquid the nearest neighboring atom distance is about 3.8
Angstrom, the second nearest is 6.1 Angstrom, and the third is 8.2 Angstrom.
Comparison of different methods
The plane fitting can fix the plane either on center of mass or center
particle. The parabolic fitting can choose normal vector via either center
of mass or center particle, and the position of the fitting surface can
be either fixed or non-fixed. Combine these three factors, there are 8
methods:
