Proton transfer in surface-stabilized chiral motifs of croconic acid

Authors

• Donna A. Kunkel, University of Nebraska-Lincoln
• James Hooper, State University of New York at Buffalo
• Scott Simpson, State University of New York at BuffaloFollow
• Geoffrey Rojas, University of Nebraska-LincolnFollow
• Stephen Ducharme, University of NebraskaFollow
• Timothy Usher, California State University
• Eva Zurek, State University of New York at BuffaloFollow
• Axel Enders, University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

2013

Citation

PHYSICAL REVIEW B 87, 041402(R) (2013); DOI: 10.1103/PhysRevB.87.041402

Comments

Copyright 2013 American Physical Society

Abstract

The structure and cooperative proton ordering of two-dimensional sheets of croconic acid were studied with scanning tunneling microscopy and first-principles calculations. Unlike in the crystalline form, which exhibits a pleated, densely packed polar sheet structure, the confinement of the molecules to the surface results in hydrogenbonded chiral clusters and networks. First-principles calculations suggest that the surface stabilizes networks of configurational isomers, which arise from direct hydrogen transfer between their constituent croconic acid monomers. Some of these configurations have a net polarization. It is demonstrated through constrained molecular dynamics simulations that simultaneous proton transfer between any two molecules can occur spontaneously. This finding is a prerequisite for the occurrence of in-plane ferroelectricity based on proton transfer in 2D sheets.