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NCONV

Masoud Nahali
masoudnahali@gmail.com

Dear Firefly Users

I have used "NCONV=4.5" in my input for the SCF convergence. It means that the convergence is reached when the density change between two consecutive SCF cycles is less than 10^(-4.5) or 3*10^(-5).

the lines below is one of my SCF steps :

ITER EX DEM  TOTAL ENERGY      E CHANGE  DENSITY CHANGE    DIIS ERROR      INTEGRALS   SKIPPED
* * *   INITIATING DIIS PROCEDURE   * * *
1  0  0 -3654.010061008 -3654.010061008   0.027738005   0.006150221             -1        -1
2  1  0 -3654.010871171    -0.000810163   0.023518159   0.022479261             -1        -1
3  2  0 -3654.013930379    -0.003059209   0.008856269   0.008333109             -1        -1
4  3  0 -3654.013534182     0.000396198   0.005316080   0.003565101             -1        -1
5  4  0 -3654.014225050    -0.000690868   0.001903469   0.005148299             -1        -1
6  5  0 -3654.014368343    -0.000143293   0.000956684   0.002133792             -1        -1
7  6  0 -3654.014404861    -0.000036518   0.000503151   0.000987793             -1        -1
8  7  0 -3654.014412598    -0.000007738   0.000385881   0.000328227             -1        -1

-----------------
DENSITY CONVERGED
-----------------

As it is clear 0.000385881 > 3*10^(-5) ; so why the density was converged ? Is there another criteria to reach the convergence ?

Is the "NCONV=4.5" logical when my "OPTTOL" value is 0.0001 ?

I appreciate your help in advance to understand the convergence criteria better.

Best Wishes

Masoud
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Masoud Nahali, Sharif University of Technology

Tue Jan 25 '11 4:41pm