Abstract:
Formation of exotic electronic states driven by electron correlations is one of the most
intriguing phenomena in condensed matter physics. The macroscopic properties of a material
are a consequence of how electrons and atoM.S. are arranged and held together in
a solid. The motion of electrons and nuclei is well described by laws of quantum mechanics.
The coupling between electronic charge, spin and lattice degree of freedom at
microscopic level dictates the behavior of a material. With the theoretical and experimental
advances, it has become possible to understand and control materials at di erent
length and time scales, and with the recent advances in computational resources and
scienti c algorithM.S., materials can be designed and their response to external stimuli
can be understood through computer simulations. This gives us a better understanding
of structure-property relationship in materials. The introduction of Density functional
theory by Kohn and Sham [1] marked a breakthrough in rst-principles computational
techniques. First-principles density functional theory based simulations provide fundamental
insights into structural stability and properties of a material under the in
uence
of external stimuli. The physical properties of a material such as electronic structure,
stress, elastic constant, polarization and vibrational properties can be estimated with
reliable accuracy using rst-principles approach. On the other hand, classical atomistic
modeling of materials helps in the study of their properties at long length and time scales through use of Monte Carlo simulations, possibly with a rst-principles based e ective
Hamiltonian. This thesis is divided into two parts based on the kind of materials used
for various technological applications. Part I consists of Chapter 3 and Chapter 4,
focuses on Organic-Inorganic Hybrid Perovskites for solar cell technology. Part II consists
of Chapter 5 which focuses on Excitonic Insulators: an exotic class of long-range
interacting system. A brief introduction to them is given below.
