Title 



Theory of elastic and piezoelectric effects in twodimensional hexagonal boron nitride
 
Author 



 
Abstract 



Starting from an empirical force constant model of valence interactions and calculating by Ewalds method the ionion force constants, we derive the dynamical matrix for a monolayer crystal of hexagonal boron nitride (hBN). The phonon dispersion relations are calculated. The interplay between valence and Coulomb forces is discussed. It is shown by analytical methods that the longitudinal and the transverse optical (LO and TO) phonon branches for inplane motion are degenerate at the Γ point of the Brillouin zone. Away from Γ, the LO branch exhibits pronounced overbending. It is found that the nonanalytic Coulomb contribution to the dynamical matrix causes a linear increase of the LO branch with increasing wave vector starting at Γ. This effect is general for twodimensional (2D) ionic crystals. Performing a longwavelength expansion of the dynamical matrix, we use Borns perturbation method to calculate the elastic constants (tension coefficients). Since the crystal is noncentrosymmetric, internal displacements due to relative shifts between the two sublattices (B and N) contribute to the elastic constants. These internal displacements are responsible for piezoelectric and dielectric phenomena. The piezoelectric stress constant and the dielectric susceptibility of 2D hBN are calculated.   
Language 



English
 
Source (journal) 



Physical review : B : solid state.  Lancaster, Pa, 1970  1978  
Publication 



Lancaster, Pa : 2009
 
ISSN 



05562805
 
Volume/pages 



80:22(2009), p. 224301,1224301,10
 
ISI 



000273228500045
 
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