  We propose a hypothesis that the potential energy surface (PES) of interlayer
interaction in diverse 2D materials can be universally described by the first
spatial Fourier harmonics. This statement (checked previously for the
interactions between graphene and hexagonal boron nitride layers in different
combinations) is verified in the present paper for the case of hydrofluorinated
graphene (HFG) bilayer with hydrogen bonding between fluorine and hydrogen at
the interlayer interface. The PES for HFG bilayer is obtained through density
functional theory calculations with van der Waals corrections. An analytical
expression based on the first Fourier harmonics describing the PES which
corresponds to the symmetry of HFG layers is derived. It is found that the
calculated PES can be described by the first Fourier harmonics with the
accuracy of 3\% relative to the PES corrugation. The shear mode frequency,
shear modulus and barrier for relative rotation of the layers to incommensurate
states of HFG bilayer are estimated. Additionally it is shown that HFG bilayer
is stable relative to the formation of HF molecules as a result of chemical
reactions between the layers.
