Secondment to the Rocasolano Institute of Physical Chemistry
Carolina Cruz participated in the secondment at the Institute of Physical Chemistry “Rocasolano”. The purpose was to perform Molecular Dynamics (MD) simulations on LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator) under the supervision of Prof. Enrique Lomba. This was an extension of the theoretical work done during the past two years of a system that consists of a mixture of ionic liquid (IL) and neutral solvent that can phase separate below its upper critical point. During the first months of the secondment, Carolina learned Python programming language, became familiar with the basics aspects of LAMMPS, ran some trial simulations of the studied system, and checked the thermodynamic consistency of the obtained results by implementing python-written codes.
Regarding her research, as a first task, bulk simulations were conducted to explore the phase behavior of the system in the canonical ensemble (NVT) with a number of particles N=4000, total density p=0.8, and pressure P=8.
The Lennard-Jones potential was implemented in addition to a Coulombic pairwise interaction with a cut-off radius: rcLJ=1.12 and rcCol=4.0. The researchers were interested in finding the conditions at which the mixture phase separates into a phase rich in ionic liquid and a phase rich in the solvent. In order to determine whether the phase separation takes place, the structure factor was calculated, S(q), which gives information on the spatial correlations between particle positions. The code to do such calculations was provided by prof. Lomba. At the phase separation, the structure factor diverges. Phase separation was found at temperatures T=2.73 and T=2.66 for the parameters mentioned above.
In the next step on the molecular simulations work, Carolina is planning to introduce walls with a certain electrostatic potential and simulate the confined system to tackle the effects of confinement and external electric fields in order to assess the influence of demixing on differential capacitance.
3 Nov.2019 - 30 Aug. 2020