title: Structural studies of the bond-orientational order and hexatic-smectic transition in liquid crystals of various compositions.
abstract: We report on the X-ray studies of freely suspended hexatic films of three different liquid crystal compounds. By applying angular X-ray cross-correlation analysis (XCCA) to the measured diffraction patterns the parameters of the bond-orientational (BO) order in the hexatic phase were directly determined. The temperature evolution of the BO order parameters was analyzed on the basis of the multicritical scaling theory (MCST). Our results confirmed the validity of the MCST in the whole temperature range of the existence of the hexatic phase for all three compounds. The temperature dependence of the BO order parameters in the vicinity of the hexatic-smectic transition was fitted by a conventional power law with a critical exponent β ≈ 0.1 of extremely small value. We found that the temperature dependence of higher order harmonics of the BO order scales as the powers of the first harmonic, with an exponent equal to the harmonic number. This indicates a nonlinear coupling of the BO order parameters of different order. We demonstrate that compounds of various compositions, possessing different phase sequences at low temperatures, display the same thermodynamic behavior in the hexatic phase and in the vicinity of the smectic-hexatic phase transition.
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22607 Hamburg, Germany. ivan.vartaniants@desy.de and National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Kashirskoe shosse 31, 115409 Moscow, Russia.
authors.forename: I A
authors.initials: IA
authors.lastname: Zaluzhnyy
authors.affiliation: European XFEL GmbH, Holzkoppel 4, D-22869 Schenefeld, Germany.
authors.forename: R P
authors.initials: RP
authors.lastname: Kurta
authors.affiliation: FSRC "Crystallography and Photonics", Russian Academy of Sciences, Leninskii prospect 59, 119333 Moscow, Russia. ostrenator@gmail.com.
authors.forename: E A
authors.initials: EA
authors.lastname: Sulyanova
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22607 Hamburg, Germany. ivan.vartaniants@desy.de.
authors.forename: O Yu
authors.initials: OY
authors.lastname: Gorobtsov
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22607 Hamburg, Germany. ivan.vartaniants@desy.de.
authors.forename: A G
authors.initials: AG
authors.lastname: Shabalin
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22607 Hamburg, Germany. ivan.vartaniants@desy.de.
authors.forename: A V
authors.initials: AV
authors.lastname: Zozulya
authors.affiliation: National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Kashirskoe shosse 31, 115409 Moscow, Russia.
authors.forename: A P
authors.initials: AP
authors.lastname: Menushenkov
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22607 Hamburg, Germany. ivan.vartaniants@desy.de.
authors.forename: M
authors.initials: M
authors.lastname: Sprung
authors.affiliation: Department of Chemistry, University of Warsaw, Zwirki I Wigury 101, 02-089, Warsaw, Poland.
authors.forename: A
authors.initials: A
authors.lastname: Krówczyński
authors.affiliation: Department of Chemistry, University of Warsaw, Zwirki I Wigury 101, 02-089, Warsaw, Poland.
authors.forename: E
authors.initials: E
authors.lastname: Górecka
authors.affiliation: FSRC "Crystallography and Photonics", Russian Academy of Sciences, Leninskii prospect 59, 119333 Moscow, Russia. ostrenator@gmail.com and Landau Institute for Theoretical Physics, Russian Academy of Sciences, prospect akademika Semenova 1-A, 142432 Chernogolovka, Russia.
authors.forename: B I
authors.initials: BI
authors.lastname: Ostrovskii
authors.affiliation: Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22607 Hamburg, Germany. ivan.vartaniants@desy.de and National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Kashirskoe shosse 31, 115409 Moscow, Russia.
authors.forename: I A
authors.identifier: http://orcid.org/0000-0002-0340-8234
authors.initials: IA
authors.lastname: Vartanyants