Journal
PHYSICAL REVIEW B
Volume 91, Issue 20, Pages -Publisher
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.91.205433
Keywords
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Funding
- National Science Foundation of China [11204305, U1230202(NSAF)]
- special Funds for Major State Basic Research Project of China (973) [2012CB933702]
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We report a hierarchical first-principles investigation on the entangled effects of lattice dimensionality and bond characteristics in the lattice dynamics of silicene and germanene. It is found that bond bending (stretching) negatively (positively) contributes to Gruneisen constant gamma, which results in the negative acoustic (positive optical) gamma. The layer thickening (bond weakening) caused by chemical functionalization tends to increase (decrease) the acoustic (optical) gamma, due to the increased (decreased) bond-stretching effect. The excitation of the negative-gamma modes results in negative thermal expansion, while mode excitation and thermal expansion compete with each other in thermomechanics. The sensitive structural and electronic responses of silicene and germanene to functionalization help us to derive a generic physical picture for two-dimensional lattice dynamics.
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