Diffusion Monte Carlo Calculations for Rare-earths: Hartree-Fock, Hybrid B3LYP, and Long-range Corrected LC-BLYP Functional

Elkahwagy, Nagat; Ismail, A. I.; Maize, S. M. A.; Mahmoud, K. R.

doi:10.13189/ujpa.2016.100102

Cited by 2 publications

(4 citation statements)

References 19 publications

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“…However, except for Sm, the optimal value of µ for the energy of excited states is found to be at a smaller value µ =0.35 a.u. On the contrary, applying the long-range corrected scheme to BLYP functional does not improve the results for 4f-lanthanides as revealed in our previous study [8].…”

Section: Resultscontrasting

confidence: 62%

“…The electronic excitation involves a promotion of an electron with a change of spin from 6s → 5d and 7s → 6d for lanthanides and actinides respectively. The values calculated within the standard B3LYP functional for both lanthanides and actinides along with the best values calculated by employing LC-BLYP functional from our earlier work [8] are also involved for comparison.…”

Section: Resultsmentioning

confidence: 99%

“…Very recently we have tested the performance of the standard B3LYP and the long-range corrected LC-BLYP functionals for both the ground and the excited states of lanthanides and actinides [8]. Our calculations have indicated that both functionals are not suited for 4f-lanthanides which have strongly localized nature.…”

Section: Introductionmentioning

confidence: 99%

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Diffusion Monte Carlo Calculations for Rare-earths: Applying the Long-range Corrected Scheme to Minnesota M06 Functional

Elkahwagy¹,

Ismail²,

Maize³

et al. 2016

ujpa

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By employing the diffusion Monte Carlo (DMC) method, we test the success of the unpublished long-range corrected M06 (LC-M06) functional, compared to LC-BLYP functional, in improving the calculations of the ground and excited states energies for some 4f-and 5f-rare-earths at different values of the range separation parameter µ. It is found that LC-M06 functional performs well for both the ground and the excited states of 4f-lanthanides. In addition, our results reveal that the optimal value of µ for the ground state lies between 0.40-0.50 a.u. while a smaller optimal value µ =0.35 a.u. is found for the excited states. However, LC-BLYP ground and excited states results at the optimal value of µ seem to be the best for 5f-actinides.

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Section: Resultscontrasting

confidence: 62%

Section: Resultsmentioning

confidence: 99%

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Diffusion Monte Carlo Calculations for Rare-earths: Applying the Long-range Corrected Scheme to Minnesota M06 Functional

Elkahwagy¹,

Ismail²,

Maize³

et al. 2016

ujpa

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“…Such a set of rare-earth ccECPs would open new possibilities to study the broader family of RMn 6 Sn 6 with significantly improved accuracy using many-body methods such as CCSD(T), CI, QMC, and also DFT with appropriate DFAs. In fact, the current progress in applying real-space QMC to f -element systems seems to be hindered by the unavailability of accurate enough rare-earth ECPs, as we were able to find only a few QMC studies in the literature [103][104][105][106]. Therefore, we hope this work will motivate new studies in this avenue.…”

Section: Discussionmentioning

confidence: 99%

The role of electron correlations in the electronic structure of putative Chern magnet TbMn$_6$Sn$_6$ using correlated methods

Annaberdiyev¹,

Mitáš²,

Krogel³

et al. 2023

Preprint

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A member of the RMn6Sn6 rare-earth family materials, TbMn6Sn6, recently showed experimental signatures of the realization of a quantum-limit Chern magnet. Despite the promising experimental results, theoretical studies with accurate electron correlations which probe these observations have been lacking. In this work, we use quantum Monte Carlo (QMC) and density functional theory with Hubbard U (DFT+U ) calculations to examine the electronic structure of TbMn6Sn6. To do so, we optimize accurate, correlation-consistent pseudopotentials for Tb and Sn using coupled-cluster and configuration-interaction (CI) methods. We find that DFT+U and single-reference QMC calculations suffer from the same overestimation of the magnetic moments as meta-GGA and hybrid density functional approximations. Our findings point to the need for improved orbitals/wavefunctions for this class of materials, such as natural orbitals from CI, or for the inclusion of multi-reference effects that capture the static correlations for an accurate prediction of magnetic properties. The necessity for multi-reference treatment is motivated by extrapolating the dynamic correlations to the exact limit. DFT+U with Mn magnetic moments adjusted to experiment predict the Dirac crossing in bulk to be close to the Fermi level, within ∼ 120 meV, in agreement with the experiments. Our nonstoichiometric slab calculations show that the Dirac crossing approaches even closer to the Fermi level, suggesting the possible realization of Chern magnetism in this limit.

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Diffusion Monte Carlo Calculations for Rare-earths: Hartree-Fock, Hybrid B3LYP, and Long-range Corrected LC-BLYP Functional

Cited by 2 publications

References 19 publications

Diffusion Monte Carlo Calculations for Rare-earths: Applying the Long-range Corrected Scheme to Minnesota M06 Functional

Diffusion Monte Carlo Calculations for Rare-earths: Applying the Long-range Corrected Scheme to Minnesota M06 Functional

The role of electron correlations in the electronic structure of putative Chern magnet TbMn$_6$Sn$_6$ using correlated methods

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