Problems with Maximum Overlap Model (MOM)

Vladimir Rybkin rybk... at gmail.com
Mon May 15 10:55:50 CEST 2017


Dear Ivan,

according to my own experience MOM is not the most reliable approach. For 
non-trivial systems, I was never able to achieve convergence and always 
collapsed to the ground states, independently of my settings. I would not 
have high hopes if I were you.

Yours,

Vladimir

воскресенье, 14 мая 2017 г., 0:40:47 UTC+2 пользователь Ivan Infante 
написал:
>
> Hi, 
>
>   I am trying to use MOM and I have some problems.
> I start from a ground state closed-shell converged wavefunction, and I use 
> the restart file for the MOM calculation. I just de-occupy the beta HOMO to 
> occupy the LUMO beta. 
> The HOMO-LUMO gap of this system is around 2.0 eV, so there shouldnt be 
> any problem to converge the excited state. 
> However, after a few iterations, when the DIIS kicks in, it immediately 
> swaps to the ground state energy (E = -5725.1289....) .
>
>   Step     Update method      Time    Convergence         Total energy    
> Change
>
>   
> ------------------------------------------------------------------------------
>
>      1 P_Mix/Diag. 0.40E+00   13.8     0.32547826     -5724.9981579203 
> -5.72E+03
>
>      2 P_Mix/Diag. 0.40E+00   16.1     0.18145011     -5725.0429211687 
> -4.48E-02
>
>      3 P_Mix/Diag. 0.40E+00   16.0     0.11353690     -5725.0753406595 
> -3.24E-02
>
>      4 P_Mix/Diag. 0.40E+00   16.1     0.06733805     -5725.0961299910 
> -2.08E-02
>
>      5 DIIS/Diag.  0.20E-02   16.1     0.04123847     -5725.1090261343 
> -1.29E-02
>
>      6 DIIS/Diag.  0.11E-02   16.1     0.00192988     -5725.1289018949 
> -1.99E-02
>
>      7 DIIS/Diag.  0.31E-03   16.1     0.00128342     -5725.1289258147 
> -2.39E-05
>
>      8 DIIS/Diag.  0.28E-03   16.1     0.00032442     -5725.1289261285 
> -3.14E-07
>
>      9 DIIS/Diag.  0.96E-04   16.1     0.00018951     -5725.1289310034 
> -4.87E-06
>
>     10 DIIS/Diag.  0.45E-04   16.1     0.00004841     -5725.1289312796 
> -2.76E-07
>
>     11 DIIS/Diag.  0.17E-04   16.1     0.00003119     -5725.1289314498 
> -1.70E-07
>
>     12 DIIS/Diag.  0.11E-04   16.1     0.00001487     -5725.1289314674 
> -1.76E-08
>
>     13 DIIS/Diag.  0.28E-05   16.1     0.00000367     -5725.1289314718 
> -4.34E-09
>
>
>   *** SCF run converged in    13 steps ***
>
> I tried to play with the alpha mixing parameter, with a EPS_DIIS tight (to 
> avoid that the DIIS interfere) but no success:
>
>      1 P_Mix/Diag. 0.10E-03   13.8     0.32547826     -5724.9981579203 
> -5.72E+03
>
>      2 P_Mix/Diag. 0.10E-03   16.1     0.32544318     -5724.9981819920 
> -2.41E-05
>
>      3 P_Mix/Diag. 0.10E-03   16.1     0.32540810     -5724.9982060548 
> -2.41E-05
>
>      4 P_Mix/Diag. 0.10E-03   16.1     0.32537302     -5724.9982301087 
> -2.41E-05
>
>      5 P_Mix/Diag. 0.10E-03   16.1     0.32533795     -5724.9982541538 
> -2.40E-05
>
>      6 P_Mix/Diag. 0.10E-03   16.1     0.32530289     -5724.9982781901 
> -2.40E-05
>
>      7 P_Mix/Diag. 0.10E-03   16.1     0.32526782     -5724.9983022175 
> -2.40E-05
>
>      8 P_Mix/Diag. 0.10E-03   16.1     0.32523276     -5724.9983262361 
> -2.40E-05
>
>      9 P_Mix/Diag. 0.10E-03   16.1     0.32519771     -5724.9983502459 
> -2.40E-05
>
>     10 P_Mix/Diag. 0.10E-03   16.1     0.32516265     -5724.9983742469 
> -2.40E-05
>
>     11 P_Mix/Diag. 0.10E-03   16.1     0.32512760     -5724.9983982391 
> -2.40E-05
>
>     12 P_Mix/Diag. 0.10E-03   16.1     0.32509256     -5724.9984222225 
> -2.40E-05
>
>     13 P_Mix/Diag. 0.10E-03   16.1     0.32505752     -5724.9984461970 
> -2.40E-05
>
>     14 P_Mix/Diag. 0.10E-03   16.1     0.32502248     -5724.9984701628 
> -2.40E-05
>
>     15 P_Mix/Diag. 0.10E-03   16.1     0.32498745     -5724.9984941198 
> -2.40E-05
>
>     16 P_Mix/Diag. 0.10E-03   16.1     0.32495242     -5724.9985180680 
> -2.39E-05
>  
>  Here it seems that is converging, but the EPS_SCF remains very high. 
> When I use intermediete values of ALPHA, like 0.1 or 0.05, the calculation 
> goes slow, but tends still to converge to the ground state. 
>
> Is there something that I can use to converge my calculation to the 
> excited state ? 
>
> Thanks, 
> Ivan
>
>
>
>
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