Theory of molecular opto-electronics VII. Effective hyperpolarizability in the hexamine crystal

M. Hurst, R. W. Munn, J. O. Morley

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Since crystals of hexamine (hexamethylenetetramine or urotropine) contain only one molecule in the primitive unit cell, the effective polarizability and first hyperpolarizability of the molecule in the crystal are uniquely determined by the crystal linear and quadratic susceptibility. The effective polarizability is found to be 15.5 × 10-40 Fm2 (equivalent to 14.0 × 10-24 cm3) and the local-field factor 1.511. Different reported quadratic susceptibilities imply hyperpolarizabilities βxyz from 0.96 × 10-51 to 10.4 × 10-51 Fm3V-1 (0.26 × 10-30-2.8 × 10-30 esu). Sum-over-states CNDOVSB calculations of βxyz do not converge even after 250 states, when βxyz is only 0.14 × 10-30 esu. Possible reasons for the discrepancy include applying the CNDOVSB method to a non-conjugated molecule for which it is not designed, environmental effects and phonon effects. This first direct comparison of a crystal effective hyperpolarizability and a theoretical free-molecule hyperpolarizability nevertheless confirms the value of theory for order-of-magnitude predictions.

    Original languageEnglish
    Pages (from-to)15-19
    Number of pages5
    JournalJournal of Molecular Electronics
    Volume6
    Issue number1
    Publication statusPublished - Jan 1990

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