I have a problem about PAW_GGA

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zzzhong · #1 Post by **zzzhong** » Fri Jul 22, 2005 3:29 am

Hello, everyone
I want to calculate GaMnAs system. I want to use PAW_GGA pseudopotential. First, I want to validate PAW_GGA pseudopotential. I calculate bulk GaAs using Ga and As potpaw_GGA. I get that bulk GaAs lattice constant is about 5.76 angstrom, but 5.65 in experiment. Is the LDA resulted? Next, I use Ga and As PAW pseudopotential. I get that bulk GaAs lattice constant is about 5.64 that is very near exmperimental value. Is the PAW_GGA something wrong? Any replies and explains are appreciated. Thanks

Best regard.
zzzhong

Sorry , maybe I should post in physics question. But I donnot know to delete old thread.
<span class='smallblacktext'>[ Edited ]</span>

Veronika · #2 Post by **Veronika** » Mon Jul 25, 2005 6:30 am

GGA overestimates lattice constants in general. You have only 1.9 % deviation from the experimental value, so that is not too much anyway. I do not know about your calculational setup (k points, accuracy, etc. ) but imho you can't "improve" your result very much ...

greetings