[Wien] some queries from 2Doptimization

[Dr. K. C. Bhamu]

Dear Wien2k Users,

I finished lattice parameter optimization with 2Doptimize (set2D) script
for AFM case.

I gave me a nice parabola fit for MB Eqn.

At the end of ana2D_lapw I see below parameters




#####################################
Vol-opt= 6477.2543 ,  coa-opt= 2.4690

a0= 13.7918 , c0= 34.0519 bohr
a
*0= 7.2983 , c0= 18.019 Ang     *

*or    a0=13.79178818 c0= 34.050975
Bohr--------------------------------------------------------------------
Say this is Eqn.-(1)*




then "parabolfit_lapw -t 2 -scf '*.scf'" gave me below parameters (the pink
and blue may be "a" and "c", respectively):


AFM.ene and AFM.latparam generated
 Enter dimension of fit (number of variable lattice parameters, 1-6):
           2  fitcase           6  parameter
 lowest data point:  -197507.047435900        14.3863200000000
   35.5987000000000
          36  -197506.997315480       -197506.995255490
  -197506.995195780       -197506.989177860       -197506.989866030
  -197506.979961790       -197507.046392950       -197507.044306660
  -197507.045024960       -197507.038881620       -197507.040400960
  ************** skipping some data here************
  -197506.841649710       -197507.039826230       -197507.041358040
  -197506.834684780       -197506.829326540       -197507.031120700
  -197506.824849460

     I     INITIAL X(I)        D(I)

     1    -0.197507D+06     0.100D+01
     2     0.100000D+00     0.102D+01
     3     0.143863D+02     0.600D+00
     4     0.100000D+00     0.761D+01
     5     0.355987D+02     0.608D+00
     6     0.100000D+00     0.155D+01

    IT   NF      F       RELDF   PRELDF   RELDX  MODEL  STPPAR  D*STEP
NPRELDF

     0    1 0.848D+00
     1    2 0.261D-02 0.10D+01 0.10D+01 0.2D-05    G   0.0D+00 0.7D+00
0.10D+01
     2    3 0.121D-03 0.95D+00 0.96D+00 0.2D-06    G   0.0D+00 0.1D+00
0.96D+00
     3    4 0.109D-03 0.10D+00 0.10D+00 0.2D-08    G   0.0D+00 0.9D-03
0.10D+00

 ***** X-CONVERGENCE *****

 FUNCTION     0.108736D-03   RELDX        0.210D-08
 FUNC. EVALS       4         GRAD. EVALS      24
 PRELDF       0.100D+00      NPRELDF      0.100D+00

     I      FINAL X(I)        D(I)          G(I)

     1   -0.197507D+06     0.100D+01    -0.319D-06
     2    0.172755D+00     0.129D+01     0.251D-04
     3    0.144346D+02     0.411D+00     0.223D-05
     4    0.102224D-01     0.822D+01    -0.376D-06
     5    0.357076D+02     0.608D+00    -0.462D-08
     6    0.382409D-01     0.187D+01    -0.262D-07
 Parabolic equation of state:         info           3
 E = x1 + x2(a-x3)^2
        + x4(b-x5)^2 + x6(a-x3)(b-x5)
Fitparameter are
    -197507.051608          0.172755         14.434559
0.010222     ------------------                 *Say this is Eqn.-(2)*

         35.707596          0.038241
         lattic parameters       energy         de(EOS)
      14.021960      34.697070 -197506.997315       0.001500
      13.929700      35.158170 -197506.995255       0.001373
************** skipping some data here************


My queries are:

1. I did not relax the forces for optimization as there always be some
forces due to lattice strains if we optimize the structure. So I wish to
relax the structure with these parameters and then wish to do further
calculations. Am I right?

2. Why there is the difference between the lattice parameters obtained in
Eqn.(1) and Eqn. (2), and which data I should consider for further
calculations/

3. The B-M Eqn fit gave me below parameters:
V0,B(GPa),BP,E0      6477.0172        25.2686         5.0558
-197507.048851

while in graph obtained from B-M. Eqn I see a slight variation in these
parameters:
V0,B(GPa),BP,E0   6477.6387, 24.7964, 5.7605, -197507.048792


4. In the link (provided below) for 2Doptimization, it is mentioned for
clmextrapol_lapw that "Convert it to #clmextrapol_lapw for SP case"

As my case is AFM and I did not follow this instruction, how it may
influence mine optimizes lattice parameters?


 http://susi.theochem.tuwien.ac.at/reg_user/textbooks/2Doptimize.pdf
<http://susi.theochem.tuwien.ac.at/reg_user/textbooks/2Doptimize.pdf>


It would be nice for me if I  get inlined reply.



Kind regards

Bhamu
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