Ring-puckering potential energy functions for cyclobutane and related molecules based on refined kinetic energy expansions and theoretical calculations

•Theoretical calculations were used to model the ring-puckering vibration.•Refined and reliable kinetic energy functions were calculated for these vibrations.•Remarkable agreement between theory and experiment.•The observed vibrational transition frequencies were fit well with the PEFs.•Excellent results for nine ring molecules and many of their isotopic species.