mirror of https://github.com/phonopy/phono3py.git
33 lines
1.4 KiB
Markdown
33 lines
1.4 KiB
Markdown
This is the example of NaCl calculation. Since all atoms are displaced, to
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obtain force constants, an external force constants calculator is necessary,
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i.e., built-in force constants calculator has no ability to compute force
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constants for such dataset. In this example, ALM is used. See
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https://phonopy.github.io/phonopy/setting-tags.html#alm. The easiest way to
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install ALM is to use conda.
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The supercell is 2x2x2 of the conventional unit cell. The VASP calculation was
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made for force calculations with 500 eV, 2x2x2 off-Gamma-centre k-point sampling
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mesh for the supercell, and PBE-sol. For dielectric constant and Born effective
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charges were calculated in a similar calculation settings with `LEPSILON =
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.TRUE.` and 4x4x4 off-Gamma-centre k-point sampling mesh.
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200 supercells were generated with random displacements of 0.03 A displacement
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distance. The calculated forces, displacements, dielectric constant, and Born
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effective charges are all stored in `phono3py_params_NaCl222.yaml.xz`.
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Force constants are calculated by
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```
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% phono3py-load phono3py_params_NaCl222.yaml.xz -v --alm
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```
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This calculation may require a few minutes depending on computer hardware and
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some amount of memory space. By this `fc2.hdf5` and `fc3.hdf5` are obtained. The
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lattice thermal conductivity at 300 K is calculated by
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```
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% phono3py-load phono3py_params_NaCl222.yaml.xz --mesh 50 --ts 300 --br
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```
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The result is ~7.3 W/m-K at 300 K.
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