Abstract
Topochemical transformations of layered materials CaX2 (X=Si, Ge) are the method of choice for the high-yield synthesis of pristine, defect-free two-dimensional systems silicane and germanane, which have advanced electronic properties. Based on solid-state dispersion-corrected calculations, mechanisms for such transformations are elucidated that provide an in-depth understanding of phase transition in these layered materials. While formation of such layered materials is highly favorable for silicane and germanane, a barrier of 1.2 eV in the case of graphane precludes its synthesis from CaC2 topochemically. The energy penalty required for distorting linear acetylene into a trans-bent geometry accounts for this barrier. In contrast it is highly favorable in the heavier analogues, resulting in barrierless topochemical generation of silicane and germanane. Photochemical generation of the trans-bent structure of acetylene in its first excited state (S1) can directly generate graphane through a barrierless condensation. Unlike the buckled structure of silicene, the phase-h of CaSi2 with perfectly planar silicene layers exhibits the Dirac cones at the high symmetry points K and H. Interestingly, topochemical acidification of the cubic phase of calcium carbide is predicted to generate the previously elusive platonic hydrocarbon, tetrahedrane.
Original language | English (US) |
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Pages (from-to) | 18454-18460 |
Number of pages | 7 |
Journal | Chemistry - A European Journal |
Volume | 21 |
Issue number | 50 |
DOIs | |
State | Published - Dec 7 2015 |
Bibliographical note
Publisher Copyright:© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Keywords
- Group 14 elements
- layered materials
- metal carbides
- phase transitions
- tetrahedrane