### Abstract

We study theoretically polydiacetylene chains diluted in their monomer matrix. We employ the density-matrix renormalisation group method (DMRG) on finite chains to calculate the ground state and low-lying excitations of the corresponding Peierls-Hubbard-Ohno Hamiltonian that is characterised by the electron transfer amplitude t 0 between nearest-neighbours, by electron-phonon coupling constant α, by Hubbard interaction U, and by long-range interaction V. We treat lattice relaxation in the adiabatic limit, i.e., we calculate the polaronic lattice distortions for each excited state. We present accurate DMRG results for the single-particle gap, the singlet exciton, the triplet ground state and its optical excitation, and find a good agreement with experimental data for PDA-3BCMU chains. Using a fairly stiff spring constant, the length of our unit cell is about 1% larger than observed in experiment.

Original language | English |
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Pages (from-to) | 2506-2515 |

Number of pages | 10 |

Journal | Molecular Physics |

Volume | 111 |

Issue number | 16-17 |

DOIs | |

Publication status | Published - Sep 1 2013 |

### Keywords

- Peierls-Hubbard-Ohno model
- density-matrix renormalisation group
- exciton
- polydiacetylene
- spectrum

### ASJC Scopus subject areas

- Biophysics
- Molecular Biology
- Condensed Matter Physics
- Physical and Theoretical Chemistry

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## Cite this

*Molecular Physics*,

*111*(16-17), 2506-2515. https://doi.org/10.1080/00268976.2013.809164