Benzene molecule

This tutorial explains how to optimize the geometry by using different algorithms. In this tutorial, a benzene molecule is placed in a cubic box with the cell edges of 10 Angstrom. pot_C.pbe1 and pot_H.pbe1 are used with the cutoff energies of 36 Ry (GMAX=6) and 400 Ry (GMAXP=20) for the wave functions and the argmentation charge, respectively.

  • Input file (nfinp_1)
         0     0     0     0     0     0 : I_CTRL(1:6) (DUMMY)
      6.00 20.00     2    12    12       : GMAX GMAXP NTYP NATM NATM2
        25     0                         : NUM_SPACE_GROUP TYPE_BRAVIS_LATTICE
     18.89726878 18.89726878 18.89726878 90.0 90.0 90.0 : A B C ALPHA BETA GAMMA
         1     1     1     1     1     1 : K_MESH
         1     0                         : NCORD NINV
             0.0000000000        2.6366036317        0.0000000000     1     1     1
            -2.2833569864        1.3182923672        0.0000000000     1     1     1
            -2.2833569864       -1.3182923672        0.0000000000     1     1     1
             0.0000000000       -2.6366036317        0.0000000000     1     1     1
             2.2833569864       -1.3182923672        0.0000000000     1     1     1
             2.2833569864        1.3182923672        0.0000000000     1     1     1
             0.0000000000        4.6909824123        0.0000000000     1     1     2
            -4.0624970473        2.3454912062        0.0000000000     1     1     2
            -4.0624970473       -2.3454912062        0.0000000000     1     1     2
             0.0000000000       -4.6909824123        0.0000000000     1     1     2
             4.0624970473       -2.3454912062        0.0000000000     1     1     2
             4.0624970473        2.3454912062        0.0000000000     1     1     2
      6.00  0.15 28.29     3     1  0.00 : TYPE IATOMN ALFA AMION ILOC IVAN ZETA1
      1.00  0.15 28.29     3     1  0.00 : TYPE IATOMN ALFA AMION ILOC IVAN ZETA1
         0     0     0     0     0       : ICOND INIPOS INIVEL ININOS INIACC
         0     1                         : IPRE IPRI
       300   300     0    28000.00     0 : NMD1 NMD2 LAST_ITER CPUMAX IFSTOP
         6     1                         : WAY_MIX MIMX_WHAT
         0     8  0.80                   : ITER_START KBXMIX  MIX_ALPHA
      0.60  0.50  0.60  0.70  1.00       : DTIM1 DTIM2 DTIM3 DTIM4 DTIM
    500.00     4     1    0.10D-08       : DTIO IMDALG IEXPL EDELTA
    0.0010    0.10D-03     0             : WIDTH FORCCR ISTRESS
    ggapbe           1                   : XCTYPE KSPIN
      1.00                               : DESTM
       101                               : NBZTYP
         4     4     4                   : (DUMMY)
         4     4     4                   : (DUMMY)
        18                               : KEG
         1                               : NEXTST
         0                               : (DUMMY)
         2                               : IMSD
         0                               : EVALUATE_EKO_DIFF
         0                               : NPDOSAO
         0  0.00                         : SM_N DOPPING
    In this example, the GDIIS method is used (IMDALG=4) with the time step of 500 atomic unit. The GDIIS method works fine, when the atomic positions are close to the equilibirium. A rule of thumb is to switch from quenched molecular dynamics (IMDALG=2) to GDIIS when the maximum force becomes smaller than 1.e-2. Note that in the current implementation, GDIIS method does not work when the optimization step exceeds the 3 * N, where N is the number of atoms.
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