Yakobson, Boris I.2021-05-032021-11-012021-052021-04-30May 2021Su, Tonghui. "DFT methods applications in nanoscale materials modeling." (2021) Master’s Thesis, Rice University. <a href="https://hdl.handle.net/1911/110437">https://hdl.handle.net/1911/110437</a>.https://hdl.handle.net/1911/110437With the development of simulation methods and explorations in the first-principle calculation, the density functional theory methods have more applications that could predict the properties and explain the results from the nanoscale scope for the experiments. Here, in this thesis, we utilized the DFT methods for the simulation of the material to explore their performance in molecular, 1D, and 2D systems. All these examples showed the precise of single-molecule configurations and also the periodic system properties. In the first molecular system, we combined the geometric configurations with the energy conversion, which converts the photoexcitation energy to mechanical energy output in the type of geometric transform. The DFT methods help to find the pathway in this process and got the numeric efficiency for the system. And we could also summarize a principle to connect the spring constant of a molecule with the mechanical efficiency. In the second example, which is about 1D Se nanowire, we utilized the SWCNT to provide the environment for Se nanowire synthesis and explore the mechanical stability after the encapsulation effects. Also, more stable configurations in SWCNT provides more important properties like charge carrier mobility for nanoscale devices application. With electronic properties and band structure calculation, we discovered Rashba effects in 3H configuration and used strain to control the parameter of Rashba splitting in the band structure, which set the basis and another option for 1D light element spintronics devices. In the third example, monolayer MoS2 with Cu atom doping, we use first-principle calculation collaborating with experiment to provide the microscopic structure exploration, like the doping type and substitutional sites for fixed stoichiometry and also the phase diagram with different potential energy for a different source. With these calculations, we could have a thorough picture of Cu doped MoS2 from both macroscopic and microscopic structures and properties. Our work here shows the important use for DFT calculation for many kinds of systems and properties exploration, which could help with more and more materials synthesis and potential applications.application/pdfengCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.DFTMaterials simulationLow-dimensional materialsThesis2021-05-03