# 2D materials and defects: adventures in atomic-scale simulations

# 2D materials and defects: adventures in atomic-scale simulations

Computational condensed matter physics has an important role to play in increasing our understanding of current materials and enabling rational design of new materials. I will show two examples of how we use first-principles quantum-mechanical calculations to simulate the properties of materials with applications in spacecraft and quantum computing.

Molybdenum disulfide (MoS_{2}) is a two-dimensional material made up of atomic sheets like graphite, which has novel optical and electronic properties. We are studying however its use as a solid lubricant with application in the low temperature and pressure environment in space, where liquid lubricants fail. It has been found that doping with transition metals can improve performance. We have studied Ni-doped MoS_{2}, to determine a phase diagram of energetically favorable sites for Ni atoms, how these dopant structures can be detected with IR and Raman spectroscopy, and how doping can cause phase transitions among polytypes. Work is also underway to design a Course Undergraduate Research Experience (CURE) based on calculations of 2D materials.

Systems with unpaired electron spins, including magnetic molecules and defects in solids, are being investigated as quantum bits (qubits) or quantum photon emitters for quantum computing and quantum information applications. Understanding of the ground and excited states of these systems are quite challenging to describe with standard electronic structure methods. I will show our new approach with the Bethe-Salpeter equation that allows more accurate and convenient calculations to explore new quantum systems, with applications to the well-studied diamond NV^{-} center defect.