QuantumATK Forum
QuantumATK => General Questions and Answers => Topic started by: faxer92 on June 5, 2018, 23:09
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Hi, ATK experts,
When computing surface energy, it's very easy to hit dipole polarization in slab.
In VASP, people can correct this dipole issue by setting interior function (-LDIPOL).
But, how to overcome this issue in ATK?
A symmetric mirror-slab method is often proposed in ancient papers,
https://www.researchgate.net/post/How_do_I_avoid_polarization_in_surface_energy_calculation_using_DFT (https://www.researchgate.net/post/How_do_I_avoid_polarization_in_surface_energy_calculation_using_DFT)
how to apply this in my case, i.e., asymmetric structure of o-phase HfO2.
much appreciate for your assistance.
===========================
data_global
_cell_length_a 5.23
_cell_length_b 5.04
_cell_length_c 5.06
_cell_angle_alpha 90
_cell_angle_beta 90
_cell_angle_gamma 90
_symmetry_space_group_name_H-M 'P -1'
loop_
_symmetry_equiv_pos_as_xyz
'x,y,z'
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
Hf 0.968 0.733 0.743
Hf 0.468 0.267 0.743
Hf 0.032 0.267 0.243
Hf 0.532 0.733 0.243
O 0.111 0.068 0.888
O 0.389 0.068 0.388
O 0.611 0.932 0.888
O 0.889 0.932 0.388
O 0.733 0.463 0.992
O 0.767 0.463 0.492
O 0.233 0.537 0.992
O 0.267 0.537 0.492
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In the QuantumATK, this issue can be resolved in an natural way by using non-periodic, Dirichlet (Neumann) boundary condition imposed on the left (right) boundary in the left (right) vacuum region of the slab configuration, as described in the following tutorial, https://docs.quantumwise.com/tutorials/work_function_ag_100/work_function_ag_100.html.
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Thanks Petr,
I follow your indication and found new issues, i.e., GGA-PBE seems not convergence in transition metals of HfO2. LDA-PZ works but basically it gives incorrect energies of unit cell. What else can I do in this case? (some people may use LDA+PBE by QE-APL 104, 092906 (2014), but how to do that in ATK?)