I'm currently studying about the hydrogen bond's Potential Energy Surface (PES) pattern.
As per literature, single point energy obtained from Density Functional Theory (DFT) using MP2 approximation performed with Gaussian software (www.gaussian.com) showed the pattern of Lennard Jones Potential (LJ-potential). A Lennard Jones is a one-well potential http://www.cmbi.ru.nl/redock/:
However, in certain literature it is also shown to obey the double welled potential model (PES_vs._atomic-distance response).
Having said that, I'm basically wondering about the physical significance of a double-well potential model with respect to interacting-atoms, in case of hydrogen bonds. Any insight or reference towards deciphering the concerned fact would be highly appreciated.