Ab initio study of phase boundaries in disilicides MoSi2, NbSi2, TaSi2 and TiSi2
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| Year of publication | 2022 |
| Type | Conference abstract |
| MU Faculty or unit | |
| Citation | |
| Description | An ab initio analysis of MoSi2-XSi2 (X = Nb, Ta, Ti) disilicide nanocomposites was performed, where the most stable configurations of non-diffusive phase boundaries were determined as follows: MoSi2(AC)/TiSi2(DACB), MoSi2(AD)/TiSi2(CADB), MoSi2(AC)/Nb(Ta)Si2(BAC), MoSi2(AB)/ Nb(Ta)Si2(CAB) and MoSi2(AB)/Nb(Ta)Si2(ABC), where A, B, C and D denote the configurations of most densely occupied crystal planes. In the case of MoSi2(AC)/TiSi2(DACB), MoSi2(AC)/TiSi2(BDAC) and MoSi2(AC)/Nb(Ta)Si2(BAC) interfaces, the influence of defects on structure properties was studied. It was found that all structures containing the defects are stable with respect to the standard element reference states despite their destabilisation effect. This was not always true when pure disilicides were used as reference states. Furthermore, the most preferred positions of vacancies, divacancies, Al and Si impurities and vacancy-impurity couples were determined together with their formation energies. However, it was necessary to be careful during the studies of vacancies as some of them may undergo recombination with interstitial impurities, as it happened in the systems with Si impurities. The destabilisation effect of vacancies can be reduced by the presence of impurities, which leads to the conclusion that the impurities can facilitate the formation of vacancies. The diffusion (exchange of Mo-X atoms across the phase boundary) caused the stabilisation of studied structures by creating a diffusive interface in some cases. The ab initio calculations were performed using the VASP code (Vienna Ab initio Simulation Package), employing the Density Functional Theory with Projector Augmented Wave method. The exchange-correlation energy was evaluated within the Local Density Approximation with the Ceperley-Alder functional. |
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