Hello,
when studying the similar compoiunf Ce2O2S, I only had good results
usign the high-precision Ce pseudopotential
Ce.pbe-spdfn-rrkjus_psl.1.0.0.UPF from the pslibrary that includes
5s5p6s4d5d4f in valence (22 electrons in valence) and requires a
ridiculous 200 Ry cutoff to converge, despite being Ultrasoft. The U was
almost 7eV. You can find more details in this paper and its
supplementary materials :
https://pubs.acs.org/doi/abs/10.1021/acs.chemmater.9b00450 (I can send
the inout files if you want)
hth
On 29/06/2025 18:55, AISWARYA CHANDRAN via users wrote:
Dear Quantum ESPRESSO developers and users,
I am working on Ce₂O₃ and trying to reproduce the experimentally
reported band gap (~2.4–2.7 eV) using LDA+U in combination with
spin–orbit coupling (SOC) in Quantum ESPRESSO. However, despite using
U = 6 eV and including SOC via fully relativistic pseudopotentials,
the computed band gap is significantly underestimated (around 1.1 eV).
Here are the key points of my setup:
- Code version: QE 7.X
- Pseudopotential: Ce.pz-spdfn-rrkjus_psl.1.0.0.UPF (fully relativistic)
- Functional: PZ-LDA
- Hubbard_U applied: U = 6.0 eV on Ce 4f
- Calculation type: SCF → bands
- Structure: 5-atom primitive cell from literature (a = 3.87 Å, c/a =
1.522)
- `nbnd = 41`
- Gap is computed using `bands.x` and visual inspection
Despite these, the gap remains ~1.1 eV. Literature reports higher
values for similar setups. I also observe that relaxing the cell via
`vc-relax` makes the lattice smaller, which further reduces the gap.
Using experimental lattice constants does help, but not enough to
reach the expected values.
Could you please advise on:
1. Whether this pseudopotential is appropriate for SOC + LDA+U
calculations on Ce?
2. Any suggestions on correcting the band gap underestimation?
3. Whether a better suited pseudopotential or approach (e.g., using
GGA+U, HSE, etc.) is recommended? I am attaching the input file
4. I tried the same with Ce.pz-spdn-rrkjus_psl.1.0.0.UPF it gives band
gap of 3.7 eV. shall i proceed with spdn?
I would greatly appreciate your insights.
--
*Thanks and with Regards, *
*Aiswarya Chandran*
*Research Scholar
*
*Laboratory for Advanced Materials and Applied Research
*
*Department of Chemistry*
*NIT Calicut, Kerala, India, 673 601*
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Dr. Lorenzo Paulatto
IR IMPMC - CNRS UMR 7590 / Sorbonne Université / MNHN
phone: +33 (0)1 442 79822 / telegram: lpaulatto
http://www.impmc.upmc.fr/~paulatto/ - https://anharmonic.github.io/
23-24/423 B115, 4 place Jussieu 75252 Paris CX 05
_______________________________________________________________________________
The Quantum ESPRESSO Foundation stands in solidarity with all civilians
worldwide who are victims of terrorism, military aggression, and indiscriminate
warfare.
--------------------------------------------------------------------------------
Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
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