First-principle study on structural and electronic properties of CeO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>and ThO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>under high pressures

Song, Hong X.; Лю, Лэй; Geng, Hua-Yun; Wu, Qinghe

doi:10.1103/physrevb.87.184103

Cited by 24 publications

(14 citation statements)

References 48 publications

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“…This observation is consistent with our theoretical calculations. The unusual compressional behavior seen here is also similar to that reported in theoretical calculations for cotunnite-structured lanthanide and actinide dioxides at Mbar pressures [18][19][20]25] which we address in a later section.…”

Section: Discussionsupporting

confidence: 85%

“…Several theoretical studies have recently reported the compression behavior to megabar pressures of several AO 2 materials including CeO 2 , ThO 2 , UO 2 , and PuO 2 [18][19][20]25]. These first-principles DFT calculations show that all four compounds undergo isostructural phase transitions starting from an orthorhombic cotunnite-type structure with continuous evolution of lattice parameters.…”

Section: E Comparison With Lanthanide and Actinide Dioxidesmentioning

confidence: 99%

“…Additionally, a number of metal dioxides including TiO 2 , ZrO 2 , HfO 2 , SnO 2 , PbO 2 , CeO 2 , PuO 2 , UO 2 and ThO 2 are known or predicted to adopt the cotunnite or related structures at elevated pressures, leading to phases with very high bulk moduli or unusual compressibilities [18][19][20][21][22][23][24][25].…”

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confidence: 99%

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High-pressure polymorphism ofPbF2to 75 GPa

et al. 2016

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Lead fluoride, PbF 2 , was investigated experimentally in the laser-heated diamond anvil cell by x-ray diffraction to pressures of 75 GPa at room temperature and to 64.5 GPa and 2430 K, as well as through first-principles density functional theory calculations up to 70 GPa. During room temperature compression, no discontinuous changes in the x-ray diffraction pattern or volume were observed, but the lattice parameters display highly anomalous trends between 10-22 GPa with enhanced compressibility along the a direction and reduced or even negative compressibility along b and c. Theoretical calculations of valence electron densities at 22 GPa show that α-PbF 2 has undergone a pressure-induced isosymmetric phase transition to a postcotunnite Co 2 Si-type structure and also reveal the detailed atomic rearrangements associated with the development of an extra Pb-F bond in the high-pressure phase. Our x-ray results and theoretical calculations are consistent with an isosymmetric phase transition occurring over 10- Upon heating above 1200 K at pressures at or above 25.9 GPa, PbF 2 partially transforms to the hexagonal Ni 2 In-type phase but wholly or partially reverts back to Co 2 Si-type phase upon temperature quench. From 43-65 GPa, nearly complete transformation to the Ni 2 In-type PbF 2 is observed at high temperature, but the material partially transforms back to the orthorhombic phase upon temperature quench. Our results show that high-pressure behavior of PbF 2 is distinct from that of the alkaline earth fluorides with similar ionic radii. Our results also have relevance to understanding the behavior of lanthanide and actinide dioxides, which have been predicted theoretically to exhibit similar isosymmetric transitions at Mbar pressures.

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Section: Discussionsupporting

confidence: 85%

Section: E Comparison With Lanthanide and Actinide Dioxidesmentioning

confidence: 99%

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High-pressure polymorphism ofPbF2to 75 GPa

et al. 2016

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“…1(b). It is interesting to note that this space group is also adopted by the high-pressure phase of thorium dioxide (ThO 2 ) [42][43][44][45] . To explore the structural evolution of ThS 2 under pressure, we first pressurize the P nma phase to investigate the variation of the lattice constants.…”

Section: A Structure Identification and Characterizationmentioning

confidence: 99%

“…1 (a) and (c), respectively. It is known that the ground-state structure of ThO 2 adopts the F m3m symmetry [42][43][44][45] . We will show below that our energetic calculations also identify the F m3m phase as the ground-state structure for ThS 2 at low temperatures, but the crystal is thermodynamically driven into the P nma phase around the room temperature, which explains the experimental observation of the P nma phase of ThS 2 at ambient conditions.…”

Section: A Structure Identification and Characterizationmentioning

confidence: 99%

Structural and electronic phase transitions ofThS2from first-principles calculations

et al. 2016

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Thorium and its compounds have received considerable attention in recent years due to the renewed interest in developing the thorium fuel cycle as an alternative nuclear energy technology. There is pressing current need to explore the physical properties essential to the fundamental understanding and practical application of these materials. Here we report on a computational study of thorium disulfide (ThS2), which plays an important role in the thorium fuel reprocessing cycle. We have employed the density functional theory and evolutionary structure search methods to determine the crystal structures, electronic band structures, phonon dispersions and density of states, and thermodynamic properties of ThS2 under various pressure and temperature conditions. Our calculations identify several crystalline phases of ThS2 and a series of structural phase transitions induced by pressure and temperature. The calculated results also reveal electronic phase transitions from the semiconducting state in the low-pressure phases of ThS2 in the P nma and F m3m symmetry to the metallic state in the high-pressure phases of ThS2 in the P nma and I4/mmm symmetry. These results explain the experimental observation of the thermodynamic stability of the P nma phase of ThS2 at the ambient conditions and a pressure-induced structural phase transition in ThS2 around 40 GPa. Moreover, the present study reveals considerable additional information on the structural and electronic properties of ThS2 in a wide range of pressure and temperature. Such information provides key insights into the fundamental material behavior and the underlying mechanisms that lay the foundation for further exploration and application of ThS2.

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