QEq parameter units and example scripts

Hi all,

While working on the QEq code ( When I use REAXFF and oscillate electric field, ERROR happen - #15 by srtee ) I tried verifying what the documentation says, namely that the chi and eta parameters are given in energy units (for example kcal/mol in units real). Can any experienced QEq / ReaxFF users confirm this?

In addition, do the scripts in examples/qeq use parameters from a publication, or are they just representative numbers? If the former, it would be good to include the citation in those example files. I tried cross-checking them against some ReaxFF papers but couldn’t get a match.

1 Like

OK found the citation for examples/qeq/in.qeq.reaxc lammps/ffield.reax.cho at 166301180b80704317142b1c7ca334b8d19fb0f6 · lammps/lammps · GitHub

For units:

chi denotes the electronegativity in eV, eta denotes the self-Coulomb potential in eV, and gamma denotes the valence orbital exponent. Note that these 3 quantities are also in the ReaxFF potential file, except that eta is defined here as twice the eta value in the ReaxFF file. Note that unlike the rest of LAMMPS, the units of this fix are hard-coded to be A, eV, and electronic charge.