[Wien] MAE calculation-lack of the same symmetry like crystal structure.

[Jin Cao]

Dear Prof. Peter Blaha and wien2k users,
    excuse me for seed this message twice again because this problem is so important for me and I am very very very looking forward for your reply!!!
 
    I try to calculate the MAE of  two-layer Co2FeAl film with total energy method as mentioned in several mailing-list article. After the nosoc scf caculation, I add the soc self-consistent procedure and calculate the total energy with the direction 100, 010, 110 and -110 respectively shown as attached file.
    two-layer Co2FeAl film has 90 degree rotational symmetry of the Z axis, so the calculated MAE of 110 and -110 must be  equal to each other, but my results shown that
                                           1.  MAE of 100, -100, 010, 0-10 are always the same with each other under the same  k-points;
                                           2.  MAE of 110 and -1-10 are  are always the same with each other under the same  k-points;
                                           3.  MAE of 1-10 and -110 are  are always the same with each other under the same  k-points; 
 Main problem Here:   4.  MAE between 110 and -110 are always different with each other under the same  k-points .
I can not understand the causes of this MAE symmetry-breaking because the 110 and -110 direction has the same chemical surrounding.(check the structure file~), Has anyone came across this problem and reply to me to help me with this problem?
 
Details of My calculation:
(1)Remove the symmetry of my structure to P1(only keep one sympo. in the case.struct file).
                     The sympo. is:
                                              1      NUMBER OF SYMMETRY OPERATIONS
                                           1 0 0 0.00000000
                                           0 1 0 0.00000000
                                           0 0 1 0.00000000
                                                    1
(2)  After the nosoc scf caculation,I use the script initso_lapw to do the soc initialization, for example, i.e. 110:

                           1...... (For R-lattice in R coordinates)(default 0 0 1): 1 1 0
                           2......N  no atom without soc
                           3......Emax = 10 Ry
                           4......No RLOS
                           5......y (run symmetso)
                           6......Do you want to use the new structure for SO calculations ? (y/N)   y
Then I find the weight of every kpoint is 1 in the case.klist file which means we calculate all of the kpoints in the BZ.Then we runsp_lapw -so and compare the total energy difference between different main axis to cauculate the MAE!
       
 
My question is:
(1) Does anyone who knows the cause of non-equivalence of 110 and 1-10 direction and tell me how to solve it please~ To be honest, I have calcalated fcc-Co with the same procedure and also find the  non-equivalence of 110 and 1-10 direction!!!
 
(2)I have known that different method of throwing kpoints impact the MAE largely, and the symmetry of the system determine the way of throwing kpoints, so the symmetry may largely impact the final results, Prof. Peter Blaha has recomanded to reduce the symmetry, so I  choose P1 symmetry to cauculate MAE, is it really suitable or we need choose special symmetry for MAE calculation?
 
(3)We guess that maybe the un-converged total energy cause the energy difference under low density kpoints, so we increase the kpoints to a large density(12800 kpoints in the full BZ with P1 symmetry), but the difference is still exists, we have increased the kpoints further,but we doubt that is this guess logical?!!!
 
Thank you in advance!
 
regards,
 
Jinn
 
 
 


 












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