Layering effects on low frequency modes in n-layered MX2 transition metal dichalcogenides

Physical Chemistry Chemical Physics : PCCP
Antonio Cammarata, Tomáš Polcar

Abstract

n-Layered (n = 2, 3, 4) MX2 transition metal dichalcogenides (M = Mo, W; X = S, Se, Te) have been studied using DFT techniques. Long-range van der Waals forces have been modeled using the Grimme correction to capture interlayer interactions. We study the dynamic and electronic dependence of atomic displacement on the number of layers. We find that the displacement patterns mainly affected by a change in the layer number are low-frequency modes at Γ and A k-points; such modes are connected with the intrinsic tribological response. We disentangle electro-phonon coupling by combining orbital polarization, covalency and cophonicity analysis with phonon band calculations. We find that the frequency dependence on the number of layers and the atomic type has a non-trivial relation with the electronic charge distribution in the interlayer region. We show that the interlayer electronic density can be adjusted by appropriately tuning M-X cophonicity, acting as a knob to control vibrational frequencies, hence the intrinsic frictional response. The present results can be exploited to study the electro-phonon coupling effects in TMD-based materials beyond tribological applications.

References

Oct 28, 1996·Physical Review Letters·J P PerdewM Ernzerhof
Sep 7, 2006·Journal of Computational Chemistry·Stefan Grimme
Dec 9, 2009·The Journal of Physical Chemistry. B·Tasuku OnoderaAkira Miyamoto
Nov 17, 2010·The Journal of Physical Chemistry. B·Tasuku OnoderaAkira Miyamoto
May 1, 2012·Physical Review Letters·S CahangirovS Ciraci
Mar 21, 2013·Nature Chemistry·Manish ChhowallaHua Zhang
Sep 23, 2014·The Journal of Chemical Physics·Antonio Cammarata, James M Rondinelli
Sep 30, 2014·Nature Materials·Yongji GongPulickel M Ajayan
May 23, 2015·Inorganic Chemistry·Antonio Cammarata, Tomáš Polcar

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