### Abstract

We present calculations of the total energy per unit cell for different bond alternations of the C-C bonds bridging the distance between two aromatic rings in poly(para-phenylene vinylene) (PPV), using two different parametrizations of the energy functional in the local density approximation (LDA) and the ab initio Hartree-Fock (HF) method. For the application of correlation corrections to the HF results the system is already too large. We find that even simple LDA methods are reliable alternatives to the ab initio HF method for the calculation of potential surfaces in polymers with large unit cells. The results in turn can be used to determine parameters for model Hamiltonians necessary for theoretical studies of the dynamics of nonlinear quasiparticles in the polymers. We further present the LDA band structures of PPV together with their HF and correlation (many body perturbation theory of 2^{nd} order in Møller-Plesset partitioning, MP2) corrected counterparts. We find that the fundamental gap obtained is too large both with HF and with the correlation corrected band structure compared to experiment. However, we use only a modest correlation method and a small basis set, which already brings us to the limits of the computers available to us. The LDA gaps on the other hand are too small which, however, could be corrected with the help of self interaction corrections. None of the latter methods would lead to exceedingly large computation times.

Original language | English |
---|---|

Pages (from-to) | 73-84 |

Number of pages | 12 |

Journal | Journal of Molecular Structure: THEOCHEM |

Volume | 430 |

Issue number | 1-3 |

Publication status | Published - Apr 14 1998 |

### Fingerprint

### Keywords

- Ab initio
- DFT
- Local density approximation
- Poly(para-phenylene vinylene)

### ASJC Scopus subject areas

- Physical and Theoretical Chemistry
- Computational Theory and Mathematics
- Atomic and Molecular Physics, and Optics

### Cite this

**Energy bands and bond alternation potential in poly(para-phenylene vinylene) : A comparative ab initio quantum chemical and density functional theory study.** / Förner, Wolfgang; Bogár, F.; Knab, Reinhard.

Research output: Contribution to journal › Article

*Journal of Molecular Structure: THEOCHEM*, vol. 430, no. 1-3, pp. 73-84.

}

TY - JOUR

T1 - Energy bands and bond alternation potential in poly(para-phenylene vinylene)

T2 - A comparative ab initio quantum chemical and density functional theory study

AU - Förner, Wolfgang

AU - Bogár, F.

AU - Knab, Reinhard

PY - 1998/4/14

Y1 - 1998/4/14

N2 - We present calculations of the total energy per unit cell for different bond alternations of the C-C bonds bridging the distance between two aromatic rings in poly(para-phenylene vinylene) (PPV), using two different parametrizations of the energy functional in the local density approximation (LDA) and the ab initio Hartree-Fock (HF) method. For the application of correlation corrections to the HF results the system is already too large. We find that even simple LDA methods are reliable alternatives to the ab initio HF method for the calculation of potential surfaces in polymers with large unit cells. The results in turn can be used to determine parameters for model Hamiltonians necessary for theoretical studies of the dynamics of nonlinear quasiparticles in the polymers. We further present the LDA band structures of PPV together with their HF and correlation (many body perturbation theory of 2nd order in Møller-Plesset partitioning, MP2) corrected counterparts. We find that the fundamental gap obtained is too large both with HF and with the correlation corrected band structure compared to experiment. However, we use only a modest correlation method and a small basis set, which already brings us to the limits of the computers available to us. The LDA gaps on the other hand are too small which, however, could be corrected with the help of self interaction corrections. None of the latter methods would lead to exceedingly large computation times.

AB - We present calculations of the total energy per unit cell for different bond alternations of the C-C bonds bridging the distance between two aromatic rings in poly(para-phenylene vinylene) (PPV), using two different parametrizations of the energy functional in the local density approximation (LDA) and the ab initio Hartree-Fock (HF) method. For the application of correlation corrections to the HF results the system is already too large. We find that even simple LDA methods are reliable alternatives to the ab initio HF method for the calculation of potential surfaces in polymers with large unit cells. The results in turn can be used to determine parameters for model Hamiltonians necessary for theoretical studies of the dynamics of nonlinear quasiparticles in the polymers. We further present the LDA band structures of PPV together with their HF and correlation (many body perturbation theory of 2nd order in Møller-Plesset partitioning, MP2) corrected counterparts. We find that the fundamental gap obtained is too large both with HF and with the correlation corrected band structure compared to experiment. However, we use only a modest correlation method and a small basis set, which already brings us to the limits of the computers available to us. The LDA gaps on the other hand are too small which, however, could be corrected with the help of self interaction corrections. None of the latter methods would lead to exceedingly large computation times.

KW - Ab initio

KW - DFT

KW - Local density approximation

KW - Poly(para-phenylene vinylene)

UR - http://www.scopus.com/inward/record.url?scp=0038309686&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0038309686&partnerID=8YFLogxK

M3 - Article

VL - 430

SP - 73

EP - 84

JO - Computational and Theoretical Chemistry

JF - Computational and Theoretical Chemistry

SN - 2210-271X

IS - 1-3

ER -