mirror of https://github.com/phonopy/phono3py.git
61 lines
2.4 KiB
Plaintext
61 lines
2.4 KiB
Plaintext
This is the example of the wurtzite-type AlN phono3py calculation. The
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VASP code was used with 500 eV and LDA as XC functional. The
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experimental lattice parameters were used and the internal positions
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of atoms were relaxed by calculation. The 3x3x2 and 5x5x3 supercells
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were chosen for fc3 and fc2. The 6x6x4, 2x2x2, 1x1x2 k-point sampling
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meshes with Gamma-centre in the basal plane and off-Gamma-centre along
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c-axis were employed for the unit cell, fc3 supercell, and fc2
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supercell, respectively. For the DFPT calculation of Born effective
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charges and dielectric constant, the 12x12x8 k-point sampling mesh
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with the similar shift was used.
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Perfect and displaced supercells were created by
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% phono3py --dim="3 3 2" -c POSCAR-unitcell -d
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Then the forces were calculated with the above settings. FORCES_FC3
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and FORCES_FC2 were created with subtracting residual forces of
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perfect supercell from all displaed supercell forces by
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% phono3py --cf3 disp-{00001..01254}/vasprun.xml --cfz disp-00000/vasprun.xml
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In the example directory, FORCES_FC3 is compressed to FORCES_FC3.lzma.
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After unzipping FORCES_FC3.lzma, to obtain fc3.hdf5 and normal fc2.hdf5,
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% phono3py --sym-fc
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Using 13x13x9 sampling mesh, lattice thermal conductivity is calculated by
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% phono3py --mesh="13 13 9" --fc3 --fc2 --br
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kappa-m13139.hdf5 is written as the result. The lattice thermal
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conductivity is calculated as k_xx=228.2 and k_zz=224.1 W/m-K at 300 K.
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With --nac option, non-analytical term correction is applied reading
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the Born effective charges and dielectric constant from BORN file:
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% phono3py --mesh="13 13 9" --fc3 --fc2 --br --nac
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This changes thermal conductivity at 300 K to k_xx=235.7 and
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k_zz=219.1. The shape of phonon band structure is important to
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fullfill energy and momentum conservations.
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Use of larger supercell of fc2 may change the shape of phonon band structure.
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To see it, first regenerate phono3py_disp.yaml with --dim-fc2 option,
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% phono3py --dim="3 3 2" --dim-fc2="5 5 3" -c POSCAR-unitcell -d
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To create force constants, FORCES_FC2 is needed.
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% phono3py --cf2 disp-{00001..00006}/vasprun.xml --cfz disp-00000/vasprun.xml
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Then re-create force constants and calculate thermal conductivity,
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% phono3py --sym-fc
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% phono3py --mesh="13 13 9" --fc3 --fc2 --br --nac
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k_xx=236.0 and k_zz=222.2 are obtained. In the case of this example,
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we can see that the larger fc2 supercell contributes little, which
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means that the 3x3x2 supercell was good enough to obtain a good shape
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of phonon band structure.
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