Quasiparticle and excitonic gaps of one-dimensional carbon chains.
We report diffusion quantum Monte Carlo (DMC) calculations of the quasiparticle and excitonic gaps of hydrogen-terminated oligoynes and extended polyyne. The electronic gaps are found to be very sensitive to the atomic structure in these systems. We have therefore optimised the geometry of polyyne by directly minimising the DMC energy with respect to the lattice constant and the Peierls-induced carbon-carbon bond-length alternation. We find the bond-length alternation of polyyne to be 0.136(2) Å and the excitonic and quasiparticle gaps to be 3.30(7) and 3.4(1) eV, respectively. The DMC zone-centre longitudinal optical phonon frequency of polyyne is 2084(5) cm(-1), which is consistent with Raman spectroscopic measurements for large oligoynes.
Department of Physics, Lancaster University, Lancaster LA1 4YB, UK. emostaani@gmail.com.
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E
Mostaani
TCM Group, Cavendish Laboratory, University of Cambridge, 19 J. J. Thomson Avenue, Cambridge CB3 0HE, UK and Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey, 08854-8019, USA.
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B
Monserrat
Department of Physics, Lancaster University, Lancaster LA1 4YB, UK. emostaani@gmail.com.
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Drummond
Department of Physics, Lancaster University, Lancaster LA1 4YB, UK. emostaani@gmail.com.
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Lambert