QTPIE is a fluctuating charge model that substantially improves modeling of polarization and charge transfer. I was curious whether it has ever been applied to 1D metals such as polyacetylene to provide new perspectives on topics such as Peierls' condensation and phase solitons?

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    $\begingroup$ Not answering your question, but related: all I could find is this e-print discussing the validity of QTPIE to describe the acetylene molecule. $\endgroup$
    – F'x
    May 12, 2012 at 17:33

1 Answer 1


How flattering that someone asked this question ;)

The short answer is yes, I've tried QTPIE on series of conjugated molecules like the oligoacetylenes and oligoacenes. The results, however, are fairly dismal, as can be seen in the preprint. The problem is that in these empirical charge models, the polarizability grows faster than the size of the molecule, which means that these models predict infinite polarizabilities and charge transport behavior for bulk materials, which is obviously nonsense.

The problem is quite intimately related to that of self-interaction error in approximate density functional theories, which also exhibit similar problems.

  • $\begingroup$ For para. 2, see ref. 44 of the above preprint. For SIE in DFT, see ref. 11 ibid. $\endgroup$ May 12, 2012 at 21:15
  • $\begingroup$ AcidFlask, thanks. Flattery, maybe, but the interest is genuine: I did a deep dive on 1D metal many years ago, and came away mostly unimpressed. At least two thirds of the papers were pretty much publish-now crud with no real experimental implications, and precious little insight on how to model either the chains or the solitons more accurately. I never could tell for sure if anyone had any meaningful lab evidence of the nominal fractional charges, which were usually hidden by pairing. The long-ago "almost quark finding" of 1/3 charges on levitating lumps may have been related... possibly. $\endgroup$ May 12, 2012 at 21:52
  • $\begingroup$ After some review: A genuinely interesting paper, both in its frank discussion of the fluctuation problems and in your strategy of distinguishing bare and effective electronegativities. I will be curious to see where you take such ideas as you move forward with your research. $\endgroup$ May 13, 2012 at 3:36

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