A structural modeling approach to solid solutions based on the similar atomic environment

Engineering metal-carbide hydrogen traps in steels

Hydrogen embrittlement reduces the durability of the structural steels required for the hydrogen economy. Understanding how hydrogen interacts with the materials plays a crucial role in managing the embrittlement problems. Theoretical models have indicated that carbon vacancies in metal carbide precipitates are effective hydrogen traps in steels. Increasing the number of carbon vacancies in individual metal carbides is important since the overall hydrogen trapping capacity can be leveraged by introducing abundant metal carbides in steels. To verify this concept, we compare a reference steel containing titanium carbides (TiCs), which lack carbon vacancies, with an experimental steel added with molybdenum (Mo), which form Ti-Mo carbides comprising more carbon vacancies than TiCs. We employ theoretical and experimental techniques to examine the hydrogen trapping behavior of the carbides, demonstrating adding Mo alters the hydrogen trapping mechanism, enabling hydrogen to access carbon vacancy traps within the carbides, leading to an increase in trapping capacity.

Defect modeling and control in structurally and compositionally complex materials

Conventional computational approaches for modeling defects face difficulties when applied to complex materials, mainly due to the vast configurational space of defects. In this Perspective, we discuss the challenges in calculating defect properties in complex materials, review recent advances in computational techniques and showcase new mechanistic insights developed from these methods. We further discuss the remaining challenges in improving the accuracy and efficiency of defect modeling in complex materials, and provide an outlook on potential research directions.

Local Lattice Distortion in High-Entropy Carbide Ceramics

Using the ab initio calculations, we study the lattice distortion of HfNbTaTiVC5, HfNbTaTiZrC5 and MoNbTaTiVC5 high-entropy carbide (HEC) ceramics. Results indicate that the Bader atomic radius and charge transfer in HECs is very close to those from binary carbide. The degree of lattice distortion strongly depends on the alloying element. The Bader atomic radius can excellently describe the lattice distortion in HEC. Further, the corresponding atomic radius and formation enthalpy of binary carbides may be indicators to predict the single-phase HECs.

Lattice distortion inducing local antiferromagnetic behaviors in FeAl alloys

In this work, we study the local magnetic moment as a function of order degree in solid-solution FeAl alloys. Using the combination ofab initiomethod and similar atomic environment model, we find that the decrease of magnetic moment, even antiferromagnetic behavior, of the Fe atoms derives from the distorted local atomic clusters centered at Fe atoms on the Fe-atom sublattice sites in B2 FeAl alloys. While the local magnetic moment of Fe atoms is up to 2.2μBon the Al and Fe solid-solution sublattice sites. The ordering results in the decrease of Curie temperature and magnetic moment of solid-solution FeAl alloys.