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[Xavier Gonze <gonze@pcpm.ucl.ac.be>]

Dear Pierre-Matthieu,

On 01 May 2006, at 11:07, Anglade Pierre-Matthieu wrote:

On 5/1/06, msmajdoub@uh.edu <msmajdoub@uh.edu> wrote:

Thank you for your advice!

Do you think that these values of the following parameters are reasonable?:
# Set 1 : Initial self-consistent run
iscf1 7
kptopt1 1
tolvrs1 1.0d-18 #need excellent convergence of GS quantities for RF runs

you are working with double precision floating point numbers in abinit so
tolvrs 1e-18 is almost meaning less (unless you have some non iee754 floating point numbers on your machine).
tolvrs1 1.0d-14 is already "perfect" convergence. I think you even not need that much convergence.

tolvrs 1e-18 is OK, and could be meaningful even up to about 1e-28 even with ieee754 . Indeed the way it is computed

is similar to a sum of squares of difference of double precision numbers. In the same way,

tolwfr can be meaningful to the same order of magnitude. By contrast, toldfe and toldff are simply

differences between consecutive evaluations of double precision numbers. The two latter are only meaningful

to 1e-14 usually.

Xavier