Dear Users
I have two questions:
1) I use QE5.1, and optimized CeO2 primitive cell. We all know that after
getting final optimized structure, QE does an extra scf with new cell
parameters. My last energy (with new cell parameters) and optimized one
difference is about 0.1RY. Now, do I need a new vc-relax calculation with
previous parameters as input?
this is my input cell parameter of vc-relax calculation:
=================================================
celldm(1)= 10.225308 celldm(2)= 0.000000 celldm(3)= 0.000000
celldm(4)= 0.000000 celldm(5)= 0.000000 celldm(6)= 0.000000
crystal axes: (cart. coord. in units of alat)
a(1) = ( -0.530413 0.000025 0.530403 )
a(2) = ( 0.000052 0.530414 0.530414 )
a(3) = ( -0.530413 0.530403 0.000025 )
site n. atom positions (cryst. coord.)
1 O tau( 1) = ( 0.2900000 0.2700000 0.2900000 )
2 O tau( 2) = ( -0.2500000 -0.2500000 0.7500000 )
3 Ce tau( 3) = ( 0.0000000 0.0000000 0.0000000 )
=================================================
and this is my optimized vc-relax output:
===============================
CELL_PARAMETERS (alat= 10.22530811)
-0.530413331 0.000024549 0.530403418
0.000052398 0.530413516 0.530413516
-0.530413331 0.530403418 0.000024549
ATOMIC_POSITIONS (crystal)
O 0.263099905 0.256909491 0.263099905
O -0.236877222 -0.243128052 0.763122778
Ce 0.013777317 0.006218561 0.013777317
End final coordinates
=================================
My last extra scf force and stress are (with the final optimized cell):
==============
Total force = 0.003745 Total SCF correction = 0.000000
entering subroutine stress ...
total stress (Ry/bohr**3) (kbar) P= 26.51
0.00017290 -0.00000007 -0.00000007 25.43 -0.01 -0.01
-0.00000007 0.00018388 -0.00000007 -0.01 27.05 -0.01
-0.00000007 -0.00000007 0.00018388 -0.01 -0.01 27.05
==============
2) I used ibrav=2 in above calculation, and changed the experimental positions
of one oxygen atom to change the crystal structure from its stable form (I need
to do this, because with experimental data, I always get the input structure
after doing vc-relax). Now, I need to change the primitive cell to its
conventional. I used xcrysden and VESTA, but they only show the primitive
structure. How can I change the QE output to its conventional cell.
Regards
David Foster
Ph.D. Student of Chemistry
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