howto:dft_u
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howto:dft_u [2023/11/23 09:18] – Make subscript krack | howto:dft_u [2023/11/23 10:23] (current) – Fix typo krack | ||
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====== How to run a DFT+U calculation ====== | ====== How to run a DFT+U calculation ====== | ||
- | Plain density functional theory (DFT) calculations based on the local density approximation (LDA) or the generalised gradient approximation (GGA) usually fail to describe strongly correlated system properly. LDA and GGA often incorrectly predict a metallic ground state for systems like FeO, CoO or UO< | + | Plain density functional theory (DFT) calculations based on the local density approximation (LDA) or the generalised gradient approximation (GGA) usually fail to describe strongly correlated system properly. LDA and GGA often incorrectly predict a metallic ground state for systems like FeO, CoO or UO< |
===== EOS calculation for cubic FeO using DFT+U ===== | ===== EOS calculation for cubic FeO using DFT+U ===== | ||
- | The following '' | + | The following '' |
<code cp2k> | <code cp2k> | ||
Line 222: | Line 222: | ||
&END FORCE_EVAL | &END FORCE_EVAL | ||
</ | </ | ||
+ | The suggested Hubbard U< | ||
+ | The calculations for different cell sizes, e.g. for 98% of the experimental cell volume, can be accomplished by changing the scaling factor '' | ||
+ | < | ||
+ | @SET a | ||
+ | </ | ||
+ | to | ||
+ | < | ||
+ | @SET a | ||
+ | </ | ||
+ | and likewise for other cell sizes. It recommended to start with a cell size close to the assumed minimum and to employ the wavefunction restart files consecutively for the larger and smaller cell sizes to avoid a convergence to different states for compressed and enlarged cells. | ||
+ | |||
+ | Running the example above while applying the scaling factors '' | ||
+ | < | ||
+ | # a [Angstrom] | ||
+ | 8.385257 | ||
+ | 8.444310 | ||
+ | 8.502549 | ||
+ | 8.560000 | ||
+ | 8.616690 | ||
+ | 8.672644 | ||
+ | 8.727886 | ||
+ | 8.782436 | ||
+ | 8.836318 | ||
+ | 8.889550 | ||
+ | </ |
howto/dft_u.1700731108.txt.gz · Last modified: 2023/11/23 09:18 by krack