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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 total (blue) and projected density of states (PDOS) of 6d (red), 5f (green) and 2p (black) states in Th, ThO, ThO2.
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f5: The total (blue) and projected density of states (PDOS) of 6d (red), 5f (green) and 2p (black) states in Th, ThO, ThO2.

Mentions: The projected density of states (PDOS) can provide a profound description of the electronic structures of Th, ThO and ThO2 as shown in Fig. 5. In Th and ThO, it has been found that 6d states are rather delocalized, and the 6d along with 5f states primarily govern the DOS at Ef. The 5f states mainly prevail at the conduction band with a tail entering in the valence band for ThO. A strong hybridisation between 6d and 5f states can be found in Th metal at −1 eV, which plays the most crucial role in the charge transfer which is reflected in Fig. 2. In ThO, the 6d-5f states show a peak at −1.8 eV and cut the Ef and extend to the conduction band. Once the oxidation of Th metal is initiated, the characteristics of this electronic structure altered. The introduction of oxygen to Th leads to the 6d-2p hybridisation at −8 eV, and the anti-bonding states at 2 eV and above. Under further oxidation from ThO to ThO2, the 6d-2p and 5f-2p hybridisation are pushed towards to the Ef. This can be associated with the larger crystal field splitting between 6d and 2p interaction. Overall, the oxidation does impact on the electronic structure, and it turns Th metal into an insulator ThO2. The newly found ThO combines the characteristics of Th metal and ThO2.


Stability of a new cubic monoxide of Thorium under pressure.

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

The total (blue) and projected density of states (PDOS) of 6d (red), 5f (green) and 2p (black) states in Th, ThO, ThO2.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f5: The total (blue) and projected density of states (PDOS) of 6d (red), 5f (green) and 2p (black) states in Th, ThO, ThO2.
Mentions: The projected density of states (PDOS) can provide a profound description of the electronic structures of Th, ThO and ThO2 as shown in Fig. 5. In Th and ThO, it has been found that 6d states are rather delocalized, and the 6d along with 5f states primarily govern the DOS at Ef. The 5f states mainly prevail at the conduction band with a tail entering in the valence band for ThO. A strong hybridisation between 6d and 5f states can be found in Th metal at −1 eV, which plays the most crucial role in the charge transfer which is reflected in Fig. 2. In ThO, the 6d-5f states show a peak at −1.8 eV and cut the Ef and extend to the conduction band. Once the oxidation of Th metal is initiated, the characteristics of this electronic structure altered. The introduction of oxygen to Th leads to the 6d-2p hybridisation at −8 eV, and the anti-bonding states at 2 eV and above. Under further oxidation from ThO to ThO2, the 6d-2p and 5f-2p hybridisation are pushed towards to the Ef. This can be associated with the larger crystal field splitting between 6d and 2p interaction. Overall, the oxidation does impact on the electronic structure, and it turns Th metal into an insulator ThO2. The newly found ThO combines the characteristics of Th metal and ThO2.

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.