Moirè Structures and High Throughput Calculations on Bilayers
​
Under Dr. Qunfei Zhou of Kansas University Physics, I am running high throughput calculations on 2-D materials to better understand Moirè structures
Van der Waals heterostructures have recently been at the forefront of 2 dimensional science. These structures are nothing but stackings of different monolayers that are held together by the Van der Waals force. This leads to highly tunable properties and the ability to create many exotic states.
​
Moirè structures are a special category of 2 dimensional materials, where by spatial transformation (such as rotation and or translation) a pattern appears with high symmetry. For example, in hexagonal boron nitride, we have a rotation of 1 degree for the Moirè pattern.
Note that in some areas we have nitrogen on boron, other areas boron on nitrogen, and we have everything in between as well. This leads to extremely exciting phenomena due to how the layers interact through these various stackings.
​
As of now, there is no formal framework to understand the relationship between electric potential difference and dipole moment. Understanding the relationship between these two properties is crucial to uncovering how Moirè structures behave and be able to harness these states.
​
​
Meity et al., PhysRevReserch 2, 013335, 2020
Bridges 2 Supercomputer at PSC
Example of one of the thousands bilayers built. This is AA' stacking of AsBrS. Note this is slightly shifted birds eye view
Under Dr. Zhou, I am using density functional theory to run calculations of electric potential and dipole moment on over 500 monolayers.
​
I first sorted through the C2DB database of 2 dimensional materials to only run materials that are stable and nonmagnetic. Then using python, I sorted these structures by prototype and spacegroup - two important properties that determine the symmetry of the structure. Using the ase module of python I create different stackings of each monolayer (over 2000 stackings), like the stackings we see in Moirè structures. Then using linux and bash scripting I send them to a supercomputer, bridges2, and run calculations on them with quantum espresso. Finally, I plot electric potential difference against dipole moment and look for relationships.
​
Assuming bilayers behave like capacitors, we expect a linear relationship between dipole moment and electric potential difference, which is what we see in hBN. However, it is yet to tell whether this is true for all bilayers.
​
This is an ongoing project from Summer of 2024 to present.