I managed to simulate C14 self assembled monolayers on Au(1 1 1) with LAMMPS, However at equilibrium stage, the chains stand upright(tilt angle~10). In some papers it is mentioned that tilt angle of alkanethiol SAMs are in the range of ~25-30. Do you have any idea what would be the source of this small tilt angle that I get from LAMMPS. I have checked the potential several times and temperature is constant at 300K.
Regards
Leyla Ramin
PhD student
Room S307,
School of Aerospace, Mechanical and Mechatronic Engineering,
Not enough info to guess. Could be too short a simulation
time, too close a packing, bad initial config, etc. Matt Lane
(CCd) may have additional ideas.
I managed to simulate C14 self assembled monolayers on Au(1 1 1) with
LAMMPS, However at equilibrium stage, the chains stand upright(tilt
angle~10). In some papers it is mentioned that tilt angle of alkanethiol
SAMs are in the range of ~25-30. Do you have any idea what would be the
source of this small tilt angle that I get from LAMMPS. I have checked the
potential several times and temperature is constant at 300K.
the tilting is mostly a side effect of the strength of interaction
between the alkane chains. if they don't tilt enough then there
are two likely explanations. 1) despite all your checking, your
parameters may still be wrong, e.g. missing a factor in the
interaction energy, since different MD codes handle those differently.
2) your system may be "jammed", i.e. you have to overcome
a barrier to have the chains slide into place. this can sometimes
be alleviated by running for a while at higher temperature, but
it may also be a side effect of having too small a system.
an option worth trying would be to pre-assemble the system
with the desired tilt angle and then see, if they move back to
your lower tilt angle. that should then prompt you to revisit
the potential parameters.