title: Communication: from rods to helices: evidence of a screw-like nematic phase.
abstract: Evidence of a special chiral nematic phase is provided using numerical simulation and Onsager theory for systems of hard helical particles. This phase appears at the high density end of the nematic phase, when helices are well aligned, and is characterized by the C2 symmetry axes of the helices spiraling around the nematic director with periodicity equal to the particle pitch. This coupling between translational and rotational degrees of freedom allows a more efficient packing and hence an increase of translational entropy. Suitable order parameters and correlation functions are introduced to identify this screw-like phase, whose main features are then studied as a function of radius and pitch of the helical particles. Our study highlights the physical mechanism underlying a similar ordering observed in colloidal helical flagella [E. Barry, Z. Hensel, Z. Dogic, M. Shribak, and R. Oldenbourg, Phys. Rev. Lett. 96, 018305 (2006)] and raises the question of whether it could be observed in other helical particle systems, such as DNA, at sufficiently high densities.
authors.affiliation: Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari di Venezia, Dorsoduro 2137, 30123 Venezia, Italy.
authors.forename: Hima Bindu
authors.initials: HB
authors.lastname: Kolli
authors.affiliation: Dipartimento di Scienze Chimiche, Università di Padova, via F. Marzolo 1, 35131 Padova, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Frezza
authors.affiliation: Departamento de Física Teórica de la Materia Condensada and Instituto de Física de la Materia Condensada, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Cinacchi
authors.affiliation: Dipartimento di Scienze Chimiche, Università di Padova, via F. Marzolo 1, 35131 Padova, Italy.
authors.forename: Alberta
authors.initials: A
authors.lastname: Ferrarini
authors.affiliation: Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari di Venezia, Dorsoduro 2137, 30123 Venezia, Italy.
authors.forename: Achille
authors.initials: A
authors.lastname: Giacometti
authors.affiliation: School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: Toby S
authors.initials: TS
authors.lastname: Hudson
mesh_terms: D003102:Colloids / Q000737:chemistry; D004247:DNA / Q000737:chemistry; D056004:Molecular Dynamics Simulation; D009010:Monte Carlo Method; D011108:Polymers / Q000737:chemistry
chemical_list: D003102:Colloids; D011108:Polymers; D004247:DNA