### Abstract

Calculating the enthalpy of formation of a polymer with ab initio methods requires two choices. The first decision is whether to use oligomeric extrapolation or periodic boundary conditions to model the extended system, and the second choice is between formation reactions to be modeled, for example, formation from atoms, formation from standard states, or formation from some set of molecular systems. Utilizing trans-polyacetylene and polyethylene as examples, the oligomeric and periodic techniques are contrasted, leading to a discussion of the larger than minimal unit cell required when frequency calculations only include in-phase vibrations, that is, only the k = 0 frequencies, in an enthalpy of formation calculation. The accuracy of calculating the enthalpy of formation, in light of density functional theory's increased error with larger systems and with respect to various reference states, is also discussed. The calculation of the enthalpy of formation for a polymer is most accurate when the reference states are chosen carefully and most efficient when using periodic boundary conditions.

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

Pages (from-to) | 13869-13872 |

Number of pages | 4 |

Journal | Journal of Physical Chemistry B |

Volume | 111 |

Issue number | 50 |

DOIs | |

Publication status | Published - 20 Dec 2007 |

Externally published | Yes |

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### ASJC Scopus subject areas

- Surfaces, Coatings and Films
- Physical and Theoretical Chemistry
- Materials Chemistry

### Cite this

*Journal of Physical Chemistry B*,

*111*(50), 13869-13872. https://doi.org/10.1021/jp076975o

**On calculating a polymer's enthalpy of formation with quantum chemical methods.** / Brothers, Edward; Izmaylov, Artur F.; Rusakov, Alexander A.; Scuseria, Gustavo E.

Research output: Contribution to journal › Article

*Journal of Physical Chemistry B*, vol. 111, no. 50, pp. 13869-13872. https://doi.org/10.1021/jp076975o

}

TY - JOUR

T1 - On calculating a polymer's enthalpy of formation with quantum chemical methods

AU - Brothers, Edward

AU - Izmaylov, Artur F.

AU - Rusakov, Alexander A.

AU - Scuseria, Gustavo E.

PY - 2007/12/20

Y1 - 2007/12/20

N2 - Calculating the enthalpy of formation of a polymer with ab initio methods requires two choices. The first decision is whether to use oligomeric extrapolation or periodic boundary conditions to model the extended system, and the second choice is between formation reactions to be modeled, for example, formation from atoms, formation from standard states, or formation from some set of molecular systems. Utilizing trans-polyacetylene and polyethylene as examples, the oligomeric and periodic techniques are contrasted, leading to a discussion of the larger than minimal unit cell required when frequency calculations only include in-phase vibrations, that is, only the k = 0 frequencies, in an enthalpy of formation calculation. The accuracy of calculating the enthalpy of formation, in light of density functional theory's increased error with larger systems and with respect to various reference states, is also discussed. The calculation of the enthalpy of formation for a polymer is most accurate when the reference states are chosen carefully and most efficient when using periodic boundary conditions.

AB - Calculating the enthalpy of formation of a polymer with ab initio methods requires two choices. The first decision is whether to use oligomeric extrapolation or periodic boundary conditions to model the extended system, and the second choice is between formation reactions to be modeled, for example, formation from atoms, formation from standard states, or formation from some set of molecular systems. Utilizing trans-polyacetylene and polyethylene as examples, the oligomeric and periodic techniques are contrasted, leading to a discussion of the larger than minimal unit cell required when frequency calculations only include in-phase vibrations, that is, only the k = 0 frequencies, in an enthalpy of formation calculation. The accuracy of calculating the enthalpy of formation, in light of density functional theory's increased error with larger systems and with respect to various reference states, is also discussed. The calculation of the enthalpy of formation for a polymer is most accurate when the reference states are chosen carefully and most efficient when using periodic boundary conditions.

UR - http://www.scopus.com/inward/record.url?scp=38149036459&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=38149036459&partnerID=8YFLogxK

U2 - 10.1021/jp076975o

DO - 10.1021/jp076975o

M3 - Article

VL - 111

SP - 13869

EP - 13872

JO - Journal of Physical Chemistry B Materials

JF - Journal of Physical Chemistry B Materials

SN - 1520-6106

IS - 50

ER -