Inorganic
electrides have gained remarkable attention for their
intrinsic physical properties derived from loosely bound anionic electrons.
Herein, using ab initio evolutionary structure search,
we found that the formulation of Ca and Si with the stoichiometric
ratio of 3:1 can be stabilized under mildly external pressure, where
the hexagonal P63/mmc phase is the most stable structure under a wide pressure range from
13.5 to 104 GPa. Based on the analysis of the electrostatic difference
potential as an identifier of electrides, together with the electronic
structure and electron localization function results, we have identified
the P63/mmc Ca3Si as the one-dimensional (1D) electride, whose chemical formula
could be expressed as [Ca3Si]2+:2e–. Interestingly, the electron mobility and the electron–phonon
interaction strength of P63/mmc Ca3Si electride present the strong electronic anisotropy,
illustrating the 1D electron confinement nature. Moreover, due to
the strong electron–phonon coupling between interstitial electrons
and phonons from Ca atoms, the P63/mmc Ca3Si exhibits superconductivity with a predicted
superconducting transition temperature T
c of about 17.6 K at 100 GPa, which is the highest among the already
known 1D electrides. Our works provide new insight into new thermodynamically
stable related alkaline earth based electrides and their potential
for high performance in electronics and catalytic applications.
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