Stephen Picken (DCT) in the Anniversary Edition of Liquid Crystals
12 March 2007 by TNWToday | M&CStephen Picken’s 1989 article ‘A molecular dynamics study of the nematic phase of 4-n-pentyl-4-cyanobiphenyl’ has been included in the Twentieth Anniversary Edition of Liquid Crystals. The article first appeared in Liquid Crystals, 6, 357-371 (1989). The author wrote it as part of his master''s programme in Solid State Physics under the supervision of Prof. Wim de Jeu at the University of Groningen.
The journal is marking its 20th anniversary by selecting and reprinting its 20 most significant publications. The articles in question were primarily selected on the basis of their citation index. However, the importance of their contribution, in terms of defining the field of Liquid Crystals, was also taken into account.
Each article has recently been reprinted1 and is accompanied by the author’s retrospective2 on the subsequent development of the research in question.
In his research, Stephen Picken simulated the molecular dynamics (MD) of a nematic liquid crystal, where all atoms are explicitly included in the calculations. Previously, MD simulations had only been carried out on rod-shaped model systems involving either hard repulsion or weak Van der Waals interactions.
The article describes two simulations of 64 molecules, each consisting of 19 atoms, where the partial charges define the molecular dipole moment. In contrast to real-world experiments, computer simulations make it possible to ‘switch off’ the charges. By comparing scenarios with and without a charge it is possible to demonstrate that the presence of a dipole moment leads to a broadening of the orientational distribution function. This experimental result was not properly understood at the time.
MD simulation is by now an established field within Liquid Crystals. Stephen Picken himself continued research on liquid crystals, but no longer works on MD simulations. He now concentrates on the mechanical and optical characteristics of Liquid Crystal Polymers (LCPs).
1. "A molecular dynamics study of the nematic phase of 4-n-pentyl-4''-cyanobiphenyl." S.J. Picken, W.F. van Gunsteren, P.Th. van Duynen, W.H. de Jeu, Liquid Crystals 2006, 33, 1363-1371.
2. "Switching the dipole moment for 5CB on and off", S.J. Picken, W.H. de Jeu, Liquid Crystals 2006, 33, 1359–1362.
