[QE-users] Initial density and wfc guesses from a converged calculation with coarser k mesh

[Omar Ashour]

As far as I know, this is only supported for the density/potential. The density is stored in real space and can be Fourier transformed to your finer k-grid (Fourier interpolation, more or less). The wave functions, on the other hand, are stored in k-space so there is no straightforward way to change their k-grid. 

Starting your finer grid calculation from the coarse grid density is usually better than starting from scratch, although if your original k-grid was very coarse, the Fourier interpolation to the finer grid will be poor, so your mileage may vary.  

As an aside, I believe VASP does support this using a rudimentary implementation (it just uses the wave functions at the last k-point in the coarser grid for all the extra k-points in the finer grid, which doesn't make much sense to me, especially for incommensurate grids). 

Omar A. Ashour
UC Berkeley 

> On Aug 20, 2024, at 12:05 AM, Yang Liu <rabbitkiller at 163.com> wrote:
> 
> Dear QE users
> 
> For systems hard to converge, is it possible to use the density and wfcs from a converged calculation with coarser k mesh as initial guesses for refined k mesh calculation?
> 
> I tried with "startingpot=file, startingwfc=file", but it seemd that QE accepted the density, but refused the wfcs...
> 
> Regards & Thanks
> 
> Mr. Yang Liu
> Fudan Univ., Shanghai, China
> 
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