An Ab-Initio Study of Superconductivity in LiAlB4: an MgB2-related Compound
Bibliographic record
Abstract
Superconductors have grown in importance within materials science, largely due to their applications in magnets. Despite this, the theoretical frameworks to describe most types of superconductor remain to be understood, with a key exception in BCS-type superconductors, governed by electron-phonon interactions. Here we conduct a first principles study of the BCS-type superconductor with the highest critical temperature (Tc) at ambient pressure at around 39 K, MgB2. In particular, we focus on crucial aspects of MgB2 which contribute to this Tc, including the importance of the E2g phonon mode involving in-plane vibrations of boron atoms. Through CASTEP, an analysis of the density of states at the Fermi energy is conducted, followed by a study of the vibrational properties of the material. Finally, the Eliashberg spectral function is used in tandem with the Allen-Dynes equation to calculate the Tc, demonstrated to be in good agreement with experimental studies at 39.16 K using μ∗ = 0.1. This thesis continues by introducing a new material, LiAlB4, chosen from a set of metal aluminium tetraborates and containing a similar layered structure to MgB2 with honeycomb-structured boron sheets. We find the structure to be both thermodynamically and dynamically stable, with a similar density of states at the Fermi energy as MgB2. Also displaying similar in-plane boron vibrations, LiAlB4 improves on the electron-phonon coupling strength of MgB2 to give Tc = 49.36 K at ambient pressure for μ∗ = 0.1. This is shown to largely be the result of lower frequency phonon modes related to Li vibrations, which give stronger electron-phonon coupling.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".