[Wien] [Wien]Some problems about optimize.

[Stefaan Cottenier]

I remember to have seen such behaviour before: if you take large steps in
c/a, you apparantly miss the minimum, although the curve looks smooth. For
small variations of c/a near that apparant minimum, a much steeper behaviour
appeared, with the real minimum. In my case, that real minimum was 0.1%
different from the experimental c/a, hence, I didn't investigate this
behaviour further. Don't know whether it represents physics or is an
artefact.

Stefaan

----- Original Message ----- 
From: "Yu Xie" <coffeeboy1982 at yahoo.com.cn>
To: "Wien" <wien at zeus.theochem.tuwien.ac.at>
Sent: Thursday, January 06, 2005 6:30 AM
Subject: [Wien] [Wien]Some problems about optimize.


> When I used "optimize.job" to optimize Os with constant volume and varies
c/a,the E-c/a curve was strange.
>
> For example,in the 0GPa,first,I used "3% 2% 1% 0.5% 0 -0.5% -1% -2% -3%"
to chang c/a,then I got a E-c/a curve a minimum c/a point form the
curve.Second,I used "3% 2% 1% 0.5% 0.4% 0.3% 0.2% 0.1%
0 -0.1% -0.2% -0.3% -0.4% -0.5% -1% -2% -3%" to chang c/a,I also got a E-c/a
curve and a minimum c/a point.But the two points were quite different.And
the energy couldn't fit the curve well,sometimes above it and sometimes
below it.
>
> Then I tried some other pressures,e.g.:4.97,19.91,50.39...The situation
was just like 0GPa.And I compared some c/a which got form the E-c/a
curve,some high pressure's c/a was smaller than which is below it.
>
> How can this be?Thanks.
>
> Happy new year,every wien2k users!