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Stability of a new cubic monoxide of Thorium under pressure.

Sun W, Luo W, Ahuja R - Sci Rep (2015)

Bottom Line: It is found out that the pressure can stabilize the rocksalt phase of ThO, and the transition pressure is estimated between 14 and 22 GPa.The phonon dispersion curves of the rocksalt phase show the positive frequencies which indicates its dynamical stability.Our successful prediction of the stabilization of the metallic ThO has proposed a route to synthesize novel actinide monoxides.

View Article: PubMed Central - PubMed

Affiliation: Department of Material Science and Engineering, KTH-Royal Institute of Technology, Stockholm SE-10044, Sweden.

ABSTRACT
Density functional theory has been applied to elucidate the stability of thorium monoxide (ThO). It is found out that the pressure can stabilize the rocksalt phase of ThO, and the transition pressure is estimated between 14 and 22 GPa. The stability of ThO can be attributed due to the gradually filling 5f orbitals at the expense of 7s and 6d electrons in Th metal. For ThO, the pressure induces stronger Th-O bond reflected by the newly established 6d-2p hybridization which is the dominant cause of its stability. The phonon dispersion curves of the rocksalt phase show the positive frequencies which indicates its dynamical stability. Our successful prediction of the stabilization of the metallic ThO has proposed a route to synthesize novel actinide monoxides.

No MeSH data available.


The reaction enthalpy obtained from LDA and GGA-PBE under pressure.The inner panel shows the band structures of ThO at 5 GPa (upper) and 20 GPa (lower). The weighted 6d bands are coloured in red, and the dashed dotts in black stand for O-2p bands.
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f4: The reaction enthalpy obtained from LDA and GGA-PBE under pressure.The inner panel shows the band structures of ThO at 5 GPa (upper) and 20 GPa (lower). The weighted 6d bands are coloured in red, and the dashed dotts in black stand for O-2p bands.

Mentions: To answer the above questions, the closer look at density of states is required, while so far, the mystery of stabilization ThO under pressure is still unveiled. In Fig. 4, the blurring spots are shown, and particularly the band shift in ThO under pressure is the core of the stabilization of ThO. Two different exchange-correlation (xc) functionals predict different transition pressures, and this can be used as the lower and upper limit of transition pressure. The inner panel presents the band shift of ThO under pressure, from which the origin of stabilizing ThO may be understood. At X point, the pressure forces the Th-6d and O-2p bands to mix together and this shift coincides with the 6d-2p mixing found in the stable phases of Thorium carbide and nitride30 at ambient conditions. So, we can conclude that hybridization of 6d-2p states in ThO serves as the dominant stabilizing factor.


Stability of a new cubic monoxide of Thorium under pressure.

Sun W, Luo W, Ahuja R - Sci Rep (2015)

The reaction enthalpy obtained from LDA and GGA-PBE under pressure.The inner panel shows the band structures of ThO at 5 GPa (upper) and 20 GPa (lower). The weighted 6d bands are coloured in red, and the dashed dotts in black stand for O-2p bands.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4559911&req=5

f4: The reaction enthalpy obtained from LDA and GGA-PBE under pressure.The inner panel shows the band structures of ThO at 5 GPa (upper) and 20 GPa (lower). The weighted 6d bands are coloured in red, and the dashed dotts in black stand for O-2p bands.
Mentions: To answer the above questions, the closer look at density of states is required, while so far, the mystery of stabilization ThO under pressure is still unveiled. In Fig. 4, the blurring spots are shown, and particularly the band shift in ThO under pressure is the core of the stabilization of ThO. Two different exchange-correlation (xc) functionals predict different transition pressures, and this can be used as the lower and upper limit of transition pressure. The inner panel presents the band shift of ThO under pressure, from which the origin of stabilizing ThO may be understood. At X point, the pressure forces the Th-6d and O-2p bands to mix together and this shift coincides with the 6d-2p mixing found in the stable phases of Thorium carbide and nitride30 at ambient conditions. So, we can conclude that hybridization of 6d-2p states in ThO serves as the dominant stabilizing factor.

Bottom Line: It is found out that the pressure can stabilize the rocksalt phase of ThO, and the transition pressure is estimated between 14 and 22 GPa.The phonon dispersion curves of the rocksalt phase show the positive frequencies which indicates its dynamical stability.Our successful prediction of the stabilization of the metallic ThO has proposed a route to synthesize novel actinide monoxides.

View Article: PubMed Central - PubMed

Affiliation: Department of Material Science and Engineering, KTH-Royal Institute of Technology, Stockholm SE-10044, Sweden.

ABSTRACT
Density functional theory has been applied to elucidate the stability of thorium monoxide (ThO). It is found out that the pressure can stabilize the rocksalt phase of ThO, and the transition pressure is estimated between 14 and 22 GPa. The stability of ThO can be attributed due to the gradually filling 5f orbitals at the expense of 7s and 6d electrons in Th metal. For ThO, the pressure induces stronger Th-O bond reflected by the newly established 6d-2p hybridization which is the dominant cause of its stability. The phonon dispersion curves of the rocksalt phase show the positive frequencies which indicates its dynamical stability. Our successful prediction of the stabilization of the metallic ThO has proposed a route to synthesize novel actinide monoxides.

No MeSH data available.