[Pw_forum] How to improve the precision of phonon calculation?

[Giuseppe Mattioli]

Dear Yu Hailin
The scf calculation which precedes the phonon calculation is likely poorly 
converged or the atoms are far from their equilibrium positions.
HTH

Giuseppe

On Friday, January 09, 2015 02:20:59 PM 于海林 wrote:
> The input file and resuts as shown follow:
> 
> input file:
> GaN G point phonon
> &inputph
>   tr2_ph=1.0d-14,
>   prefix='GaN',
>   epsil=.true.,
>   amass(1)=14.0037,
>   amass(2)=69.723,
>   outdir='./tempdir/',
>   fildyn='GaN.dynG',
>  /
> 0.0 0.0 0.0
> 
> 
> The results:
> 
> 
> **************************************************************************
>      freq (    1) =     -37.374010 [THz] =   -1246.662771 [cm-1]
>      freq (    2) =     -37.097882 [THz] =   -1237.452154 [cm-1]
>      freq (    3) =     -36.243849 [THz] =   -1208.964660 [cm-1]
>      freq (    4) =     -27.145266 [THz] =    -905.468612 [cm-1]
>      freq (    5) =      -6.773759 [THz] =    -225.948270 [cm-1]
>      freq (    6) =      -0.510448 [THz] =     -17.026703 [cm-1]
>      freq (    7) =       0.368416 [THz] =      12.289036 [cm-1]
>      freq (    8) =       0.600643 [THz] =      20.035301 [cm-1]
>      freq (    9) =       4.488708 [THz] =     149.727175 [cm-1]
>      freq (   10) =      25.963394 [THz] =     866.045613 [cm-1]
>      freq (   11) =      89.714931 [THz] =    2992.567990 [cm-1]
>      freq (   12) =      91.148214 [THz] =    3040.377161 [cm-1]
>  **************************************************************************
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> At 2015-01-09 14:17:44, "于海林" <yuhailin_79 at 126.com> wrote:
> 
> Dear all,
> 
> 
> I have calculated the phonon of GaN at G point. The input file and the 
results as shown follow. But the phonon results is obviously inaccuracy. 
How
> to improve the precision of phonon calculation? Thanks in advance.
> 
> 
> Best Regard!
> 
> 
> Yu Hailin
> 
> 
> College of Physics & Electronic Enginerring,
> Changshu Institute of Technology
> China

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   Giuseppe Mattioli                            
   CNR - ISTITUTO DI STRUTTURA DELLA MATERIA   
   v. Salaria Km 29,300 - C.P. 10                
   I 00015 - Monterotondo Stazione (RM)          
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