Density functional study of the electronic structure and lattice dynamics of SrCl<sub>2</sub>

Kanchana, V.; Vaitheeswaran, G.; Souvatzis, Petros; Eriksson, Olle; Lebègue, Sébastien

doi:10.1088/0953-8984/22/44/445402

Cited by 8 publications

(4 citation statements)

References 39 publications

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“…(e.g., a = 9.944 Å b = 6. 693 Å, c = 7.100 Å as opposed to experimental a = 9.907 Å, b = 6.591 Å, c = 6.974 Å), that results in lower force constants and subsequently lower vibrational frequencies. , Hence, we believe that the peak at 690 cm –1 corresponds to the plutonyl(V) ν1 stretch, while the peak at 630 cm –1 corresponds to the equatorial PuO 5 breathing mode. These Raman data represent the first measurement of the plutonyl(V) stretching frequency and can now be used as a reference going forward for the Raman investigation of other extended structure plutonyl(V) materials.…”

Section: Results and Discussionmentioning

confidence: 99%

Flux Crystal Growth of the Extended Structure Pu(V) Borate Na₂(PuO₂)(BO₃)

et al. 2023

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As part of our exploration of plutonium-containing materials as potential nuclear waste forms, we report the first extended structure Pu(V) material and the first Pu(V) borate. Crystals of Na2(PuO2)(BO3) were grown out of mixed hydroxide/boric acid flux and found to crystallize in the orthorhombic space group Cmcm with lattice parameters of a = 9.9067(4) Å, b = 6.5909(2) Å, and c = 6.9724(2) Å. Na2(PuO2)(BO3) adopts a layered structure in which layers of PuO2(BO3)2– are separated by sodium cations. Plutonium is found in a pentagonal bipyramidal coordination environment, with axial Pu(V)–O plutonyl bond lengths of 1.876(3) Å and equatorial Pu–O bond lengths ranging from 2.325(5) to 2.467(3) Å. We find that the Pu(V)–O plutonyl bond lengths are approximately 0.1 Å longer than the reported Pu(VI)–O plutonyl bond lengths and shorter by approximately 0.033 Å than the corresponding U(V) uranyl bond lengths. Raman spectroscopy on single crystals was used to determine the PuO2 + plutonyl stretching and the equatorial breathing mode frequencies of the pentagonal bipyramidal coordination environment around plutonium. Density functional theory calculations were used to calculate the Raman spectrum to help identify the Raman bands at 690 and 630 cm–1 as corresponding to the plutonyl(V) ν1 stretch and the equatorial PuO5 breathing mode, respectively. UV–vis measurements on single crystals indicate semiconducting behavior with a band gap of ∼2.60 eV.

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Section: Results and Discussionmentioning

confidence: 99%

Flux Crystal Growth of the Extended Structure Pu(V) Borate Na₂(PuO₂)(BO₃)

et al. 2023

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“…This underestimation of the gap is mainly due to the fact that GGA suffers from artificial electron self-interaction and also lack the derivative discontinuities of the exchange-correlation potential with respect to occupation number. One way to solve the band gap problem is to apply a perturbative correction to the energy levels, as in the GW approximation 31,32 . However the band gap at 60 GPa is observed to be indirect with a that LDA overbinds the system as the volume is largely underestimated which is a common feature in DFT-LDA calculations and therefore one would expect large bulk modulus.…”

Section: Resultsmentioning

confidence: 99%

“…Of course, we could expect that our band gap value might be lower than the experimental band gap, because it is well-known that first-principles calculation of the electronic structure of semiconductors and insulators using GGA gives an underestimation of the band gap values compared to experiments. − This underestimation of the gap is mainly due to the fact that GGA suffers from artificial electron self-interaction and also lacks the derivative discontinuities of the exchange-correlation potential with respect to occupation number. One way to solve the band gap problem is to apply a perturbative correction to the energy levels, as in the GW approximation. , However the band gap at 60 GPa is observed to be indirect as it occurred between the Z - and A -points. On the basis of the equilibrium crystal structures obtained at different pressures, we calculated the band gap and examined its change under hydrostatic compression.…”

Section: Resultsmentioning

confidence: 99%

High-Pressure Study of Lithium Azide from Density-Functional Calculations

et al. 2011

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The structural, electronic, optical, and vibrational properties of LiN(3) under high pressure have been studied using plane wave pseudopotentials within the generalized gradient approximation for the exchange and correlation functional. The calculated lattice parameters agree quite well with experiments. The calculated bulk modulus value is found to be 23.23 GPa, which is in good agreement with the experimental value of 20.5 GPa. Our calculations reproduce well the trends in high-pressure behavior of the structural parameters. The present results show that the compressibility of LiN(3) crystal is anisotropic and the crystallographic b-axis is more compressible when compared to a- and c-axes, which is also consistent with experiment. Elastic constants are predicted, which still awaits experimental confirmation. The computed elastic constants clearly show that LiN(3) is a mechanically stable system and the calculated elastic constants follow the order C(33) > C(11) > C(22), implying that the LiN(3) lattice is stiffer along the c-axis and relatively weaker along the b-axis. Under the application of pressure the magnitude of the electronic band gap value decreases, indicating that the system has the tendency to become semiconductor at high pressures. The optical properties such as refractive index, absorption spectra, and photoconductivity along the three crystallographic directions have been calculated at ambient as well as at high pressures. The calculated refractive index shows that the system is optically anisotropic and the anisotropy increases with an increase in pressure. The observed peaks in the absorption and photoconductivity spectra are found to shift toward the higher energy region as pressure increases, which implies that in LiN(3) decomposition is favored under pressure with the action of light. The vibrational frequencies for the internal and lattice modes of LiN(3) at ambient conditions as well as at high pressures are calculated from which we predict that the response of the lattice modes toward pressure is relatively high when compared to the internal modes of the azide ion.

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“…No thermal corrections were considered when calculating the lattice parameters from DFT, and therefore, these values correspond to 0 K. As seen in this table, lattice parameters are underestimated using LDA functional, reflecting its inherent tendency to predict stronger bonds, shorter bond lengths, and reduced unit cell volumes. In contrast, PBE calculations result in overestimated lattice parameters due to its underbinding characteristics, leading to longer bond lengths and subsequently, enlarged unit cells compared with experimental measurements, as discussed by Kanchana et al [44] Lastly, lattice constant obtained using PBEsol is also underestimated. However, the error is less than 1%.…”

Section: Computational Detailsmentioning

confidence: 95%

Effect of XC functionals and dispersion corrections on the DFT‐computed structural and vibrational properties of SrCl₂–NaCl and ZrF₄–LiF

Mofrad,

Christian,

Schorne‐Pinto

et al. 2024

J Raman Spectroscopy

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Density functional theory (DFT) calculations were performed to examine the impact of exchange–correlation (XC) functionals and van der Waals corrections (specifically the D3 method) on the structural and vibrational properties of the SrCl2–NaCl and ZrF4–LiF salt systems. Multiple XC functionals, including the local density approximation (LDA), the generalized gradient approximation using the Perdew–Burke–Ernzerhof (PBE) model, and its modified form suitable for solids (PBEsol), the dispersion‐corrected PBE‐D3 and PBEsol‐D3, were considered. Of these functionals, LDA was found to exhibit the highest degree of error, while PBEsol and PBE‐D3 displayed the least error. Underestimated lattice parameters compared with experimental values were observed to result in higher force constants, leading to an overprediction of vibrational frequencies. Conversely, an overestimation of lattice parameters was associated with lower vibrational frequencies. The methodology presented in this study yielded results that are in good agreement with experiment, irrespective of the method (finite differences vs. density functional perturbation theory) employed for calculating infrared and Raman spectra. It was further demonstrated that for alkali halides with weak Raman scattering, utilizing a supercell constructed from primitive cells better predicts Raman features than does the use of conventional cells.

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Density functional study of the electronic structure and lattice dynamics of SrCl₂

Cited by 8 publications

References 39 publications

Flux Crystal Growth of the Extended Structure Pu(V) Borate Na₂(PuO₂)(BO₃)

Flux Crystal Growth of the Extended Structure Pu(V) Borate Na₂(PuO₂)(BO₃)

High-Pressure Study of Lithium Azide from Density-Functional Calculations

Effect of XC functionals and dispersion corrections on the DFT‐computed structural and vibrational properties of SrCl₂–NaCl and ZrF₄–LiF

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Density functional study of the electronic structure and lattice dynamics of SrCl2

Cited by 8 publications

References 39 publications

Flux Crystal Growth of the Extended Structure Pu(V) Borate Na2(PuO2)(BO3)

Flux Crystal Growth of the Extended Structure Pu(V) Borate Na2(PuO2)(BO3)

High-Pressure Study of Lithium Azide from Density-Functional Calculations

Effect of XC functionals and dispersion corrections on the DFT‐computed structural and vibrational properties of SrCl2–NaCl and ZrF4–LiF

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Product

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Density functional study of the electronic structure and lattice dynamics of SrCl₂

Flux Crystal Growth of the Extended Structure Pu(V) Borate Na₂(PuO₂)(BO₃)

Flux Crystal Growth of the Extended Structure Pu(V) Borate Na₂(PuO₂)(BO₃)

Effect of XC functionals and dispersion corrections on the DFT‐computed structural and vibrational properties of SrCl₂–NaCl and ZrF₄–LiF