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Pressure-induced structural transformations and polymerization in ThC 2

View Article: PubMed Central - PubMed

ABSTRACT

Thorium-carbon systems have been thought as promising nuclear fuel for Generation IV reactors which require high-burnup and safe nuclear fuel. Existing knowledge on thorium carbides under extreme condition remains insufficient and some is controversial due to limited studies. Here we systematically predict all stable structures of thorium dicarbide (ThC2) under the pressure ranging from ambient to 300 GPa by merging ab initio total energy calculations and unbiased structure searching method, which are in sequence of C2/c, C2/m, Cmmm, Immm and P6/mmm phases. Among these phases, the C2/m is successfully observed for the first time via in situ synchrotron XRD measurements, which exhibits an excellent structural correspondence to our theoretical predictions. The transition sequence and the critical pressures are predicted. The calculated results also reveal the polymerization behaviors of the carbon atoms and the corresponding characteristic C-C bonding under various pressures. Our work provides key information on the fundamental material behavior and insights into the underlying mechanisms that lay the foundation for further exploration and application of ThC2.

No MeSH data available.


Theoretical predicted crystal structures of ThC2.(a) C2/c phase; (b) C2/m phase; (c,c′) Cmmm phase; (d,d′) Immm phase; and (e,e') P6/mmm phase. The green and brown balls represent Th and C atoms, respectively.
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f1: Theoretical predicted crystal structures of ThC2.(a) C2/c phase; (b) C2/m phase; (c,c′) Cmmm phase; (d,d′) Immm phase; and (e,e') P6/mmm phase. The green and brown balls represent Th and C atoms, respectively.

Mentions: To explore all possible phases of ThC2 under high pressures, we perform an extensive structure search through the CALYPSO code20 without any presumed structural information at 0 GPa, 50 GPa, 100 GPa, 150 GPa and 200 GPa. Further analysis on enthalpy and stability lead to five possible structural states up to 300 GPa, as illustrated in Fig. 1, which are C2/c, C2/m, Cmmm, Immm and P6/mmm as pressure goes up.


Pressure-induced structural transformations and polymerization in ThC 2
Theoretical predicted crystal structures of ThC2.(a) C2/c phase; (b) C2/m phase; (c,c′) Cmmm phase; (d,d′) Immm phase; and (e,e') P6/mmm phase. The green and brown balls represent Th and C atoms, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5382917&req=5

f1: Theoretical predicted crystal structures of ThC2.(a) C2/c phase; (b) C2/m phase; (c,c′) Cmmm phase; (d,d′) Immm phase; and (e,e') P6/mmm phase. The green and brown balls represent Th and C atoms, respectively.
Mentions: To explore all possible phases of ThC2 under high pressures, we perform an extensive structure search through the CALYPSO code20 without any presumed structural information at 0 GPa, 50 GPa, 100 GPa, 150 GPa and 200 GPa. Further analysis on enthalpy and stability lead to five possible structural states up to 300 GPa, as illustrated in Fig. 1, which are C2/c, C2/m, Cmmm, Immm and P6/mmm as pressure goes up.

View Article: PubMed Central - PubMed

ABSTRACT

Thorium-carbon systems have been thought as promising nuclear fuel for Generation IV reactors which require high-burnup and safe nuclear fuel. Existing knowledge on thorium carbides under extreme condition remains insufficient and some is controversial due to limited studies. Here we systematically predict all stable structures of thorium dicarbide (ThC2) under the pressure ranging from ambient to 300 GPa by merging ab initio total energy calculations and unbiased structure searching method, which are in sequence of C2/c, C2/m, Cmmm, Immm and P6/mmm phases. Among these phases, the C2/m is successfully observed for the first time via in situ synchrotron XRD measurements, which exhibits an excellent structural correspondence to our theoretical predictions. The transition sequence and the critical pressures are predicted. The calculated results also reveal the polymerization behaviors of the carbon atoms and the corresponding characteristic C-C bonding under various pressures. Our work provides key information on the fundamental material behavior and insights into the underlying mechanisms that lay the foundation for further exploration and application of ThC2.

No MeSH data available.