[Wien] Questions about mixing method of MSR1a

[Laurence Marks]

On Wed, Apr 3, 2013 at 9:37 AM, wxfeng at bit.edu.cn <wxfeng at bit.edu.cn> wrote:
> Dear Dr. Marks and other experienced users,
>
> I have two questions about new mixing method of MSR1a:
>
> 1) If I run the command "run_lapw –cc 0.001 –ec 0.001 –fc 1.0" together with "PORT 2.00 0.35" in case.inM, the code will terminate when the forces are less then 1.0 mRy/au or less than 2.0 mRy/au?  In my test case, the code does not terminate at 1.0 or 2.0 mRy/au, and it will still on going up to 999 iterations in which the forces are less than 0.000001 mRy/au. What is the convergent criterion of MSR1a?

Unfortunately termination of MSR1a is not ideal, although this sounds
strange and it "should" not do this. It not too large please send your
case.scf to my private email. Alternatively, do

grep -e :DIR -e GREED -e :FRMS -e :ENE -e :CHARG -e PRATT -e :DIS -e
"MIXING SC" -e PLANE *.scf > tt.txt

and send me tt.txt. (N.B., the line might get converted into two.)

>
> 2) In my mind, the mBJ is only a xc-potential and has no corresponding xc-energy, consequently the force are meaningless.  Usually the mBJ potential can not be used in geometry optimization.  While in the manual "SRC_mixer/README_5.3.pdf", I can see some statements about that MSR1a can work with mBJ potential, could you give me some hints about this?

MSR1a does not pay attention to the energy, it only uses the forces.
Hence it can "minimize" the forces with mBJ. However, it is not clear
if this is physically meaningful.

>
> Best wishes,
>
> Wanxiang Feng
>
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-- 
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu 1-847-491-3996
"Research is to see what everybody else has seen, and to think what
nobody else has thought"
Albert Szent-Gyorgi