2021 Virtual Undergraduate Research Symposium

2021 Virtual Undergraduate Research Symposium

Computational Analysis of Charge Density Motion in Strained Aluminum

Computational Analysis of Charge Density Motion in Strained Aluminum

PROJECT NUMBER: 25 | AUTHOR: Charles Matlock​, Metallurgical and Materials Engineering

MENTOR: Mark Eberhart, Chemistry

ABSTRACT

The change in the distribution of the electron density in the solid-state when a material is strained is not well understood. Computational modeling of materials in the solid-state using Density Functional Theory presents the ability to analyze how the electron density changes as the material is strained. This study utilizes molecular orbital theory and group theory in tandem with density functional theory calculations to see how the contribution of charge from the central aluminum atom changes with strain and the number of atoms. The aluminum clusters, which had an octahedral symmetry (Oh), were distorted in the T2g direction. This transforms the clusters into a D2h symmetry, eliminating the triply degenerate p-orbitals, going from Tu to a Bu symmetry. Thus, each p-orbital is non-degenerate and thus has a non-degenerate percent contribution to the Bu orbitals from the central atom. The computations were conducted using the Amsterdam Density Functional software package for clusters consisting of 19 – 79 atoms, 2 coordination shells to 5 coordination shells, which were strained by +-5%. The calculations showed consistently decreasing percent contributions from the central atom on the Bu orbitals, especially at lower strain percentages.
Future research will be conducted to analyze the results using Gradient Bundle Analysis to determine energetic changes caused by the strain to relate the change in charge density to mechanical properties, specifically the elastic modulus of aluminum.

PRESENTATION

AUTHOR BIOGRAPHY

Charles Matlock is a current senior in the Metallurgical and Materials Engineering department. He has been involved in computational research for almost 2.5 years now through the Molecular Theory Group lead by Dr. Mark Eberhart and has completed hundreds of calculations through HPC@Mines. He seeks to pursue a graduate degree, focusing on computational modeling of materials, particularly metals and ceramics. His ultimate goal in life is to develop a general model of fracture that can be used in computational models to create stronger and tougher materials.

2 Comments

  1. Hi Charles-Nice job with your poster and the delivery of your explanation. One comment on the poster. It was extremely difficult to read the axis labels on your graphs in the poster. My question regarding future work is how will you account for the effects of cluster size? Does this mean you need to repeat your calculation on much larger (and computationally expensive) clusters to get representative results?

    • Hi Doug! Thank you for your comments and questions. I didn’t notice at the time I submitted my poster that the axes were unreadable – likely because PowerPoint allowed me to zoom in much further – and I apologize.

      Regarding your question about future work, what I will likely do is create a shell cluster, that is, find the point at which the central atoms are not affected by the strain, remove them, and expand outwards. This will allow for a much larger number of atoms to be simulated, meaning there will still only be 79 atoms in the calculation, but they will be moved to outer coordination shells, thus simulating a much larger cluster without being so computationally expensive.

      The future work will also involve the use of a technique created by the Molecular Theory Group that allows for much more energetic information to be gathered from the calculations called Gradient Bundle Analysis.

      Again, thank you for your comments and questions! I hope I answered what you had asked.

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