fix bc co bond/create/angle 1 1 5 1.6 2 atype 2
With this command, 1 and 5 form a union, what is the angle? Will it be like 1 5 1?
That depends on what 1 and 5 are bound to. See the documentation:
If the atype keyword is used and if an angle potential is defined via the angle_style command, then any new 3-body interactions inferred by the creation of a bond will create new angles of type angletype , with parameters assigned by the corresponding angle_coeff command. Likewise, the dtype and itype keywords will create new dihedrals and impropers of type dihedraltype and impropertype .
This statement makes no sense.