Advances in parallel computation and algorithm implementation are leading to accurate quantum mechanical descriptions of materials systems with hundreds of atoms and thousands of electrons.  Electronic structure methods based on the density functional theory with periodic boundary conditions become the workhorse in the simulations of defects in semiconductors, interfaces, and surfaces, and noststructures.  Developments in hybrid functionals have enabled accurate description of defect levels in semiconductors and insulators, defect-related absorption and emission energies, surface and interface electronic structures.  In this presentation, it will be discussed how these advanced computational methods are employed in the discovery of novel quantum materials and their exotic properties and help guide experimental efforts in the materials characterization. Specific topics to be covered include emerging topological phases in rare-earth pnictides, embedded nanoparticles in semiconductors, defects in 2D materials, and novel interface phenomena that are promising for the next generation of electronics and spintronics.