In the reference on the dipole correction used in QE, L. Bengtsson, PRB 59,
12301 (1999), the dipole potential is given as
V_dip(z) = 4*pi*m*(z/z_m - 0.5), 0 < z < z_m
where z_m is the height of the box, and there is a discontinuity in the
potential at z = 0,z_m. I'm not sure how this fits into the QE documentation on
the dipole correction. Is V_dip in QE supposed to be something like this?:
V_dip(z) = 4*pi*m*[z/z_m - (emaxpos + eopreg -1)], emaxpos + eopreg -1 < z/z_m
< emaxpos;
= something with a steep but finite slope, otherwise
My guess is probably wrong, but the explanations in the documentation of the
roles of emaxpos and eopreg appear to be tied to the case where eamp is
nonzero. I'm not sure if the documentation for the dipfield variable is
supposed to indicate that the actual slope of the potential is supposed to be
eamp + 4*pi*m/z_m.
University of Akron
Civil Engineering (!) Dept.
