The assembly of nanosystems with organic matter and the question of understanding their electronic and dynamic properties is a problem combining both nanosciences and soft matter physics. These two fields have different paradigms, for example having different type of questions and computational techniques to answer them. More precisely, nanoscience is interested in systems that have at least one dimension of the nanometric order. These are systems with dimensions and properties that are intermediate between molecular systems and solids. Of particular interest to the research in nanosciences is the modeling of the emergence of such properties when the system size varies. On a completely different energy scale, the soft matter is formed by weakly interacting nano and molecular systems. The scale is defined with respect to room temperature; the interaction energy of the constitutive units is therefore comparable to the thermal fluctuations which plays a major role. A fundamental property is their ability to assemble in structures that have typical length scales several orders of magnitude bigger than the length scale of the unit. Despite their difference they can have complementary properties in the form of nanocomposites and their study will open the way to new materials and computational techniques.
Some nanocomposites, like polymer stabilized metal clusters or organically protected metal clusters, are ideal systems to support the exploration of novel computational techniques. The nanocomponent can play the role of a sensor since its experimental electronic properties can be used to determine the accuracy of the algorithmic developments. The following lines of research are accordingly developed in the group.
Hybrid classical-quantum simulation of stabilized metal clusters
One of the strategies to achieve the simulation of composite systems, with different length scales, consists on describing the full Hamiltonian of the system as a mixture of terms coming from approximations appropriate for every scale. The exact form and weights used distinguish the different algorithms. The correct mixture depends however strongly on the type of system under study. We have developed a code that will allow us to perform extensive tests on the possible mixing strategies for a given nanocomposite. The code is written in Python and can be freely downloaded in github. An article describing main features of the code is here.
New energy functionals for nanocomposites
Another approach, to reach a simulation of extended nanocomposites with quantum methods consists on using energy functionals that explicitely depend on the electronic density, using the local density approximation. We are currently interested in testing kinetic energy functionals since they are a major contribution to the total energy. The test systems are polymers and organic molecules that are relevant as stabilizers in nanocomposites.
Nonadiabatic relaxation dynamics of protected clusters
Recent code developments in the COMP Centre of Excellence are currently being tested to describe the relaxation dynamics of protected clusters. We aim to support further technological development of protected clusters in biosensing a biological imaging.