Rk. Ballamudi et Ia. Bitsanis, ENERGETICALLY DRIVEN LIQUID-SOLID TRANSITIONS IN MOLECULARLY THIN N-OCTANE FILMS, The Journal of chemical physics, 105(17), 1996, pp. 7774-7782
In this paper we present findings from molecular dynamics simulations
that investigated the changes induced in molecularly thin n-octane fil
ms, as a result of increasing solid-methylene unit energetic affinity.
The solid surfaces were deprived of any topographical features and we
re modeled as atomically smooth 10-4 Lennard-Jones planes. We observed
an abrupt transition in the structural features of the film at a crit
ical value of the characteristic energy that quantified the affinity b
etween solid surfaces and methylene units. The transition was signaled
by a discontinuous increase in the degree of intermolecular order and
facilitated by a precipitous extension of the octane molecules, which
adopted almost fully extended configurations. Furthermore, the transi
tion resulted in the freezing of molecular migration and rotation. The
characteristics of the transition showed that it is a mild first orde
r phase transition between a highly ordered liquid and a poorly organi
zed solid. The solid constitutes a phase with order intermediate to th
at of hydrocarbon ''rotator'' phases and two-dimensional smectics. The
se findings demonstrate that solidification of nanoscopically thin fil
ms of linear alkanes is a general, energetically driven phenomenon, wh
ich does not require the aid of commensurate surface topography. Our s
imulations provide a natural explanation for the solidlike features ex
hibited by alkane films studied experimentally. (C) 1996 American Inst
itute of Physics.