Thanks for reporting that issue. Though the input keyword ORDER is defined in the input section &BMHFTD, it is not used in the code. Only the pair potential parameters A, B, C, D, BD, and RMIN, RMAX, and RCUT are considered. It does not matter what you specify for ORDER in your input, the 6th and 8th order dispersion terms are always added using the damping parameter BD.
I will remove the unused input keyword ORDER from the &BMHFT section in the CP2K trunk version.
Paul Scherrer Institut
Dr. Matthias Krack
5232 Villigen PSI
Correct, different BD values, i.e. b(ij) parameters, are not supported currently.
It should not be too difficult to add such flexibility.
Maybe, there is no need for a code change. Did you try the following as input:
ATOMS Cl Cl
ATOMS Cl Cl
B 1.0 # does not matter
BD #any other BD value
Well, that are only warnings. The crash after a couple of MD steps could also have a different reason. Did you try one &BMHFTD section for a kind pair and compared it with a spilt &BMHFTD section using the same BD values just to be sure that the section “split” is causing the crash?
You are right, Abdullah, the resulting splined pair potentials are different. The additive behavior does not work with the same pair potential section and the same atomic kind pair twice.
I have just committed a fix which will allow for different BD values in the BMHFTD section. The pull request is currently running. You can find the fixed code already here in my fork on github.
BD 1.5 # will use 1.5 for f6 and f8
BD 1.5 2 # will use 1.5 for f6 and 2.0 for f8
There is no f7 term.