[QE-users] All-electron on-site density

[Isaacs, Eric B]

Dear all,

I want to compute the all-electron (using PAW) wavefunction squared
directly on atomic sites for semiconductor band edge states.

Since AE wavefunctions are not accessible to my knowledge, I compute
this from the difference of on-site all-electron density (obtained from
pp.x) between doped and undoped runs.

For the bulk Si conduction band, adding 1e-3 electrons to the 2-atom
primitive cell, I find the on-site density increases by 9.61e-4 /
bohr^3. This yields a |\psi|^2 value normalized by the unit-cell average
("bunching factor") of

(9.61e-4 / bohr^3) / (1e-3 / 275.97 bohr^3) = 265

where 275.97 bohr^3 is the unit-cell volume.

However, the much smaller value of 160 was obtained by two previous LAPW
studies [PRB 83, 165301 (2011), PRB 101, 115302 (2020)], and I can
obtain close values using my approach in other PAW codes (e.g., 165 in
abinit).

I am using QE v.6.7MaX with PBE and Si.pbe-n-kjpaw_psl.1.0.0.UPF. When I
significantly ramp up FFT mesh, the discrepancy remains. I tried LDA as
well as using different doping values, pseudopotentials, smearing, and
k-meshes.

Example input is attached, and I'm happy to provide additional info.

Thanks very much,
Eric Isaacs
HRL Labs

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