title: Surface Reconstructions in Organic Crystals: Simulations of the Effect of Temperature and Defectivity on Bulk and (001) Surfaces of 2,2':6',2″-Ternaphthalene.
abstract: 2,2':6',2″-Ternaphthalene (NNN) is a novel, blue-emitting material, suitable for preparation of organic light-emitting diodes. Its crystal structure has been solved recently, but its thermal behavior and surface properties have not yet been explored, partly due to the difficulty in obtaining high quality crystals. In the present study we use classical molecular dynamics to investigate the thermal behavior of bulk and (001) surfaces of NNN. Our bulk simulations indicate the occurrence of a phase transition at about 600 K. The transition is facilitated by the presence of a free (001) surface, since a reconstruction leading to a very similar structure occurs around 550 K in our surface models. This holds for both ideal and defective surface models, containing a small number of vacancies (one or two missing molecules in the outermost layer). In all cases, the process is triggered by thermal motion and involves the reorientation of the molecules with respect to the (001) plane. Both the bulk and surface phases share the monoclinic space groupP21/awith a herringbone disposition of molecules. These findings and their implications for the use of NNN in organic electronics are discussed.
authors.affiliation: Dipartimento di Chimica, Materiali e Ingegneria Chimica "G. Natta", Politecnico di Milano , Via L. Mancinelli 7, 20131 Milano, Italy.
authors.forename: Mosè
authors.initials: M
authors.lastname: Casalegno
authors.affiliation: Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca , Via R. Cozzi 55, 20125 Milano, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Moret
authors.affiliation: Institut für Festkörperphysik, Technische Universität Graz , 60101 Graz, Austria.
authors.forename: Roland
authors.initials: R
authors.lastname: Resel
authors.affiliation: Dipartimento di Chimica, Materiali e Ingegneria Chimica "G. Natta", Politecnico di Milano , Via L. Mancinelli 7, 20131 Milano, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Raos
references.citation: J Chem Theory Comput. 2008 Mar;4(3):435-47
references.pmid: 26620784
references.citation: J Am Chem Soc. 2006 Oct 18;128(41):13378-87
references.pmid: 17031949
references.citation: J Chem Phys. 2010 Apr 21;132(15):154104
references.pmid: 20423165
references.citation: ACS Nano. 2014 Jan 28;8(1):690-700
references.pmid: 24369713
references.citation: Chem Rev. 2001 Jun;101(6):1697-725
references.pmid: 11709996
references.citation: Acta Crystallogr B. 2006 Apr;62(Pt 2):330-4
references.pmid: 16552167
references.citation: Cryst Growth Des. 2011 Apr 6;11(4):1015-1020
references.pmid: 21479111
references.citation: Chem Rev. 2015 Jun 10;115(11):5570-603
references.pmid: 25970808
references.citation: Langmuir. 2007 Jul 31;23(16):8336-42
references.pmid: 17602678
references.citation: J Chem Phys. 2007 Jan 7;126(1):014101
references.pmid: 17212484
references.citation: Adv Mater. 2011 Oct 18;23(39):4532-6
references.pmid: 21901761
references.citation: J Am Chem Soc. 2003 May 21;125(20):6323-30
references.pmid: 12785866
references.citation: J Mol Graph. 1996 Feb;14(1):33-8, 27-8
references.pmid: 8744570
references.citation: J Phys Chem Lett. 2014 Apr 3;5(7):1048-54
references.pmid: 26274447
references.citation: Angew Chem Int Ed Engl. 2001 May 4;40(9):1732-1736
references.pmid: 11353494
references.citation: ACS Nano. 2014 Apr 22;8(4):3294-301
references.pmid: 24601525
references.citation: Proc Natl Acad Sci U S A. 2005 May 10;102(19):6665-70
references.pmid: 15870211
references.citation: Nature. 2001 Aug 2;412(6846):517-20
references.pmid: 11484047
references.citation: J Chem Inf Model. 2013 May 24;53(5):1191-9
references.pmid: 23621692
references.citation: Phys Rev Lett. 2005 Nov 18;95(21):215502
references.pmid: 16384154
references.citation: Adv Mater. 2013 Feb 13;25(6):878-82
references.pmid: 23184531
references.citation: Acta Crystallogr C. 2001 Aug;57(Pt 8):939-41
references.pmid: 11498620
references.citation: J Am Chem Soc. 2007 Aug 29;129(34):10316-7
references.pmid: 17672461
references.citation: J Am Chem Soc. 2006 Feb 8;128(5):1408-9
references.pmid: 16448085
references.citation: Nat Commun. 2014 Jun 11;5:4101
references.pmid: 24916130
references.citation: J Synchrotron Radiat. 2012 Sep;19(Pt 5):682-7
references.pmid: 22898945
references.citation: Phys Rev Lett. 2003 Sep 26;91(13):136102
references.pmid: 14525320
references.citation: Chem Rev. 2011 Aug 10;111(8):4833-56
references.pmid: 21417271
references.citation: ACS Nano. 2011 Oct 25;5(10):8352-6
references.pmid: 21923165
references.citation: Cryst Growth Des. 2014 Feb 5;14(2):442-449
references.pmid: 24526866
references.citation: Phys Rev Lett. 2003 May 23;90(20):206101
references.pmid: 12785907
references.citation: Chemphyschem. 2009 Aug 3;10(11):1783-8
references.pmid: 19421986
references.citation: J Chem Theory Comput. 2012 Nov 13;8(11):4556-69
references.pmid: 26605615
references.citation: Phys Rev Lett. 1992 Sep 21;69(12):1777-1780
references.pmid: 10046311
references.citation: J Phys Condens Matter. 2009 Oct 21;21(42):423101
references.pmid: 21715835
references.citation: Adv Mater. 2010 Aug 10;22(30):3242-6
references.pmid: 20535740
references.citation: Nat Commun. 2014 Nov 07;5:5400
references.pmid: 25377483