# name
The NH3-NH3 intermolecular interaction: the (NH3)2-5 small ammonia clusters and liquid ammonia

# metadata.dc.description[].value
Treballs Finals de Grau de Química, Facultat de Química, Universitat de Barcelona, Any: 2015, Tutora: Margarita Albertí Wirsing

# metadata.dc.description.abstract[].value
Molecular Dynamics (MD) is a simulation technique that allows to analyse the interactions
between atoms and molecules along the time, giving a visualization of the movement of the
particles. For this simulation, an energy potential model describing the interaction needs to be
implemented in MD programmes, giving us information directly comparable with experimental
behaviour. MD simulations not only are useful for comparative purposes but also for predictive
ones. Obviously, if we want to make predictions with a high guarantee of success, the model
must be accurate. However, in order to reduce the simulation computational cost, the model has
to be as simple as possible.
Ammonia is one of the most important compounds in nature because it contributes
significantly to the nutritional needs of living organisms. In recent years, there have been a large
number of accurate theoretical as well as experimental investigations on small ammonia
clusters interactions, but not so many about liquid ammonia.
In order to represent big systems with lots of molecules (as required to simulate liquids), it is
very important to have a function describing as good as possible the intermolecular interactions.
In MD the previous interaction is often expressed as a sum of electrostatic and non electrostatic
interaction contributions. The electrostatic one is usually defined by the Coulomb’s law equation,
whereas the non electrostatic one is often given by the Lennard Jones (LJ) potential. The LJ
function, although it is quite good and widely used in MD simulations, it presents some
problems. It is too repulsive at short distances, and too attractive at long distances. For this
reason, the present TFG focuses on the study of ammonia using a modified LJ potential energy
function (ILJ) to describe the non electrostatic contribution.
The ammonia study, according to the different properties of small clusters and liquid
ammonia, has been divided in two parts. In the first one, the binding energy and equilibrium
geometry of some small clusters, (NH3)2-5, have been calculated using the ILJ function and the
results have been compared with other theoretical as well as experimental data. In the second
part, once the reliability of the potential energy function has been proved, it has been applied to investigate some characteristics of liquid ammonia. In particular, the evolution of the density
values and of the diffusion coefficients with the temperature has been analysed. Moreover some
structural properties of liquid ammonia have been compared with X-ray and neutron diffraction experimental data.

# metadata.dc.title[].value
The NH3-NH3 intermolecular interaction: the (NH3)2-5 small ammonia clusters and liquid ammonia

# metadata.dc.title.alternative[].value
Interacció intermolecular NH3-NH3: Petits clústers d'amoníac, (NH3)2-5, i amoníac líquid