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I am trying to figure out how to set the initial wavefunction in VASP, on the VASP wiki page of INIWAV, it is said that VASP would fill wavefunction arrays with random numbers.

INIWAV=1
Fill wavefunction arrays with random numbers. 

Does INIWAV=1 mean the occupation number of each wavefunction orbital is random?

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    $\begingroup$ I am assuming this refers to random coefficients of planewaves etc, but admittedly I don't know enough to properly answer. I suspect someone will know exactly what this really does. $\endgroup$ Dec 10, 2021 at 23:05
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    $\begingroup$ I also believe that INIWAV = 1 assigns random coefficients on the wavefunctions. Occupancy of orbitals should be controlled by other tags, like ISMEAR, etc. $\endgroup$
    – che_kid
    Dec 12, 2021 at 15:31

1 Answer 1

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No, it randomly chooses the different plane-wave coefficients $c_{Gbk}$ for wavevector $G$, of each trial Kohn-Sham state at each band $b$ and k-point $k$,

$\psi_{bk}(r)=\sum_G c_{gbk}e^{iG.r}$.

The occupation of those states, $f_{bk}$, will be chosen differently. In fact, in a non-self-consistent method, the initial occupations are not important, since they are only used in constructing the output density,

$\rho_{out}(r)=\sum_{bk}f_{bk}|\psi_{bk}(r)|^2,$

at which point the trial eigenvalues are known and the occupations may be assigned following the Fermi-level search and pseudo-thermal occupation.

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