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Giant electron-phonon interactions in molecular crystals and the importance of nonquadratic coupling

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Monserrat, B 
Engel, EA 
Needs, RJ 


We investigate electron-phonon coupling in the molecular crystals CH4, NH3, H2O, and HF, using first-principles quantum mechanical calculations. We find vibrational corrections to the electronic band gaps at zero temperature of -1.97 eV, -1.01 eV, -1.52 eV, and -1.62 eV, respectively, which are comparable in magnitude to those from electron-electron correlation effects. Microscopically, the strong electron-phonon coupling arises in roughly equal measure from the almost dispersionless high-frequency molecular modes and from the lower frequency lattice modes. We also highlight the limitations of the widely used Allen-Heine-Cardona theory, which gives significant discrepancies compared to our more accurate treatment.



cond-mat.mtrl-sci, cond-mat.mtrl-sci

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Physical Review B - Condensed Matter and Materials Physics

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American Physical Society (APS)
Engineering and Physical Sciences Research Council (EP/J017639/1)
Engineering and Physical Sciences Research Council (EP/K014560/1)
Engineering and Physical Sciences Research Council (EP/F032773/1)
EPSRC (1208472)
B.M. acknowledges Robinson College, Cambridge, and the Cambridge Philosophical Society for a Henslow Research Fellowship. E.A.E. and R.J.N. acknowledge financial support from the Engineering and Physical Sciences Research Council (EPSRC) of the UK [EP/K013688/1]. The calculations were performed on the Cambridge High Performance Computing Service facility and the Archer facility of the UK's national high-performance computing service (for which access was obtained via the UKCP consortium [EP/K013564/1]).