Symmetry and the polar state of condensed molecular matter

Hulliger, Jürg; Wüst, Thomas; Rech, Mathias (2013). Symmetry and the polar state of condensed molecular matter. Zeitschrift für Kristallographie, 228(12), pp. 607-610. Oldenbourg 10.1524/zkri.2013.1654

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Polar molecular crystals seem to contradict a quantum mechanical statement, according to which no stationary state of a system features a permanent electrical polarization. By stationary we understand here an ensemble for which thermal averaging applies. In the language of statistical mechanics we have thus to ask for the thermal expectation value of the polarization in molecular crystals. Nucleation aggregates and growing crystal surfaces can provide a single degree of freedom for polar molecules required to average the polarization. By means of group theoretical reasoning and Monte Carlo simulations we show that such systems thermalize into a bi-polar state featuring zero bulk polarity. A two domain, i.e. bipolar state is obtained because boundaries are setting up opposing effective electrical fields. Described phenomena can be understood as a process of partial ergodicity-restoring. Experimentally, a bi-polar state of molecular crystals was demonstrated using phase sensitive second harmonic generation and scanning pyroelectric microscopy

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Departement of Chemistry and Biochemistry

UniBE Contributor:

Hulliger, Jürg; Wüst, Thomas and Rech, Mathias

Subjects:

500 Science > 570 Life sciences; biology
500 Science > 540 Chemistry

ISSN:

0044-2968

Publisher:

Oldenbourg

Language:

English

Submitter:

Franziska Bornhauser-Rufer

Date Deposited:

04 Apr 2014 23:16

Last Modified:

05 Dec 2014 07:15

Publisher DOI:

10.1524/zkri.2013.1654

Uncontrolled Keywords:

Bi-polar state; Condensed molecular matter; Electrical polarization; Monte Carlo simulation; Thermal equilibrium; Symmetry

BORIS DOI:

10.7892/boris.46831

URI:

https://boris.unibe.ch/id/eprint/46831

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