Defect-induced properties of MoSi2/Nb(Ta)Si2 disilicide nanocomposites

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Authors	VŠIANSKÁ Monika PAVLŮ Jana ŠOB Mojmír
Year of publication	2024
Type	Article in Periodical
Magazine / Source	Materials Today Communications
MU Faculty or unit	Faculty of Science
Citation
web	https://www.sciencedirect.com/science/article/pii/S2352492824005646?via%3Dihub
Doi	http://dx.doi.org/10.1016/j.mtcomm.2024.108584
Keywords	Disilicides; C11(b) MoSi2; C40 NbSi2; C40 TaSi2; Nanocomposites; Interfaces; Vacancies; Si and Al impurities; Segregation energies
Description	Research on disilicide nanocomposites, as modern materials with promising technological applications, is very desirable these days. Our ab initio analysis concentrates on the C11(b) (tetragonal) MoSi2/C40 (hexagonal) NbSi2 or TaSi2 nanocomposites containing 12 types of interfaces formed by (110) planes in the C11(b) and (0001) planes in the C40 disilicide. The most stable nanocomposites are MoSi2(AC)/Nb(Ta)Si-2(BAC), MoSi2(AB)/Nb(Ta)Si-2(CAB) and MoSi2(AB)/Nb(Ta)Si-2(ABC). The interfaces reveal positive formation energies, e.g. gamma(BA)(IF) = 0.63670 J.m(-2) and gamma(CA)(IF) = 0.63727 J.m(-2) in the Nb system and gamma(BA)(IF) = 0.57837 J.m(-2) and gamma(CA)(IF) = 0.57802 J.m(-2) in the Ta system. In the most stable C(11)b-MoSi2(AC)/C40-Nb(Ta)Si-2(BAC) nanocomposite, the effect of the impurities (Al, Si), vacancies or their aggregates on the stability and structure is investigated. It turns out that (i) vacancies preferentially form at the Si positions in the third (first) layer of MoSi2 in the Nb (Ta) systems, utilising an energy of 2.259 eV.Va(-1) (1.971 eV. Va(-1)); (ii) Al impurities prefer Si positions, and it is easier to introduce them into the Ta system than into the Nb one; however, this does not apply if Al is in the Mo position; (iii) Si impurities prefer Ta positions to Nb ones, and the bulk to interfacial ones; (iv) the Si-Si divacancy is the least destabilising among divacancies; and (v) Al impurities in both systems prevent the formation of Si vacancies, and the Si impurities simplify the formation of vacancies in the Nb system. As there is very little experimental information on the structure and properties of these interfaces, most of the present results are theoretical predictions which may motivate future experimental work.