Thermodynamic stability and electronic structure of thorium boron carbides
Abstract
This work presents a study of the thermodynamic stabilities of the thorium boron carbides including a revised version of the Th-B binary system: (i) a maximum of 1 at.% Th dissolves in beta boron, (ii) the “hectoboride ThB 66 (O)” is found at ThB 60 , (iii) the B-rich boundary of the hexaboride Th 1-x □ x B 6 (□ denotes a vacancy) extends according to its homogeneity region 0≤x≤0.22, (iv) novel thorium diboride with AlB 2 -type (a = 0.310(1) nm, c = 0.402(1) nm) forms in a peritectic reaction at 2200±50°C. Based on DFT derived energies of formation, thermodynamic phase equilibria in the binary system Th-B have been calculated i.e. phase relations have been defined for Th-B up to the melting range. For all ternary Th-B-C compounds, density functional theory calculations were made within the pseudopotential approach of VASP utilizing a general gradient approximation for the exchange correlation functional. A metaGGA approach was then applied to all compounds in their equilibrium structures, which significantly lowered the enthalpies of formation for ThC and ThC 2 , whereas it had only a small impact on ThB 4 . Atomic volumes and charges were computed by the concept of Bader and distinctly ionic features are derived consisting of Th +2 , B +1 , B -½ , C -1 , C -2 and C -3 ions. All compounds are, however, of metallic character.
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BibTeX
@article{podloucky2026thermodynamic,
title = {{Thermodynamic stability and electronic structure of thorium boron carbides}},
author = {Raimund Podloucky and Jan Vřeštál and Pavel Brož and Gerald Giester and Henri Noël Bernard and Peter Rogl},
journal = {Solid State Sciences},
year = {2026},
month = oct,
doi = {10.1016/j.solidstatesciences.2026.108428},
url = {https://hal.science/hal-05834627v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - Thermodynamic stability and electronic structure of thorium boron carbides
AU - Raimund Podloucky
AU - Jan Vřeštál
AU - Pavel Brož
AU - Gerald Giester
AU - Henri Noël Bernard
AU - Peter Rogl
PY - 2026
DA - 2026/10/22
JO - Solid State Sciences
DO - 10.1016/j.solidstatesciences.2026.108428
UR - https://hal.science/hal-05834627v1
AB - This work presents a study of the thermodynamic stabilities of the thorium boron carbides including a revised version of the Th-B binary system: (i) a maximum of 1 at.% Th dissolves in beta boron, (ii) the “hectoboride ThB 66 (O)” is found at ThB 60 , (iii) the B-rich boundary of the hexaboride Th 1-x □ x B 6 (□ denotes a vacancy) extends according to its homogeneity region 0≤x≤0.22, (iv) novel thorium diboride with AlB 2 -type (a = 0.310(1) nm, c = 0.402(1) nm) forms in a peritectic reaction at 2200±50°C. Based on DFT derived energies of formation, thermodynamic phase equilibria in the binary system Th-B have been calculated i.e. phase relations have been defined for Th-B up to the melting range. For all ternary Th-B-C compounds, density functional theory calculations were made within the pseudopotential approach of VASP utilizing a general gradient approximation for the exchange correlation functional. A metaGGA approach was then applied to all compounds in their equilibrium structures, which significantly lowered the enthalpies of formation for ThC and ThC 2 , whereas it had only a small impact on ThB 4 . Atomic volumes and charges were computed by the concept of Bader and distinctly ionic features are derived consisting of Th +2 , B +1 , B -½ , C -1 , C -2 and C -3 ions. All compounds are, however, of metallic character.
SN - 1293-2558
ER -