Density functional theory studies of Yb-, Ca- and Sr-substituted Mg2NiH4 hydrides

Highlights
- The rare-earth and alkaline-earth metals play important roles in MMgNiH4.
- Two possible decomposition reactions of MMgNiH4 are discussed in details.
- Vibration properties suggest that MMgNiH4 hydrides are kinetically stable.
- The decomposition temperature of SrMgNiH4 is higher than those of YbMgNiH4 and CaMgNiH4.