Diffusion timescales for DBAZ white dwarfs with DBAZ atmosphere
models as boundary condition (D. Koester 2020)
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The atmosphere models, which provide the boundary conditions for the
envelopes, use the latest code with a number of improvements (e.g. a
more accurate treatment of molecule formation, more absorption
processes), which are most important at the cool end of the sequence.
The envelope code is a completely new development, described in more
detail in Koester et al. (2020, A&A 635,103).  The diffusion code has
been completely rewritten. Major changes are the inclusion of nonideal
effects in the diffusion equation after Beznogov & Yakovlev (2013,
Phys. Rev. E, 111, 161101), new calculations for the collision
integrals by Stanton & Murillo (2016, Phys.Rev. E, 93, 043203), and
the Thomas-Fermi mean ionization model for the determination of
average charges of all elements at higher densities.  In the current
version the average charges are calculated from the Saha equation
(including nonideal effects) for log density < -3.0 and from the TF
model for log densities >-2.0 g/cm3. In the intermediate region a
smooth transition is provided.

The DBAZ calculations use ML2/alpha=0.8 for the convection in
atmosphere and envelope. The hydrogen abundance is [H/He] = -4.50 (log
number abundances). The atmosphere models include the 15 most
important elements (Z = 1,2,6,7,8,10,11,12,13,14,15,16,20,26,28)
consistently with Bulk Earth composition relative to Ca, which is used
as metallicity parameter. The envelope models include only H and He,
since the trace elements have no influence on the structure. However,
the sinking time scales are calculated for 30 elements at the border
of the convection zone (optionally including 1 Hp overshoot).

Structure of tables:
OV0 = no overshoot, OV1 one Hp overshoot
DBAZ_difftable825_OV1:  log g = 8.25, 1 Hp overshoot

first line: Teff, log g, overshoot
second line: metallicity parameter [Ca/He] from -7 to -15
third line: fractional mass log q of the convection zone
remaining lines: log taudiff for elements Z=3 to 30.