# Research Data Supporting "Novel Phases of Copper Phosphides from Computational Structure Searches"
## Abstract
Using first principles structure searching we identify a novel $Fm\bar{3}m$ phase of Cu$_2$P and two low-lying metastable structures, an $I\bar{4}3d$-Cu$_3$P phase, and a $Cm$-Cu$_3$P$_{11}$ phase. Pair distribution functions of the novel $Cm$-Cu$_3$P$_{11}$ phase show its structural similarity to the experimentally identified $Cm$-Cu$_2$P$_7$ phase. The relative stability of all Cu-P phases at finite temperatures is determined by calculating the Gibbs Free energy using vibrational effects from phonon modes at 0 K. From this, a finite-temperature convex hull is created, on which $Fm\bar{3}m$-Cu$_2$P is dynamically stable and the Cu$_{3-x}$P ($x\ll1$) defect phase $Cmc2_1$-Cu$_8$P$_3$ remains metastable (within 10 meV/atom of the convex hull) across a temperature range from 0 K to 600 K. Both CuP$_2$ and Cu$_3$P exhibit theoretical gravimetric capacities higher than contemporary graphite anodes. The predicted Cu$_2$P composition has a theoretical gravimetric capacity of 508 mAh/g as a Li-ion battery electrode, greater than both Cu$_3$P (363 mAh/g) and graphite (372 mAh/g). Cu$_2$P is also predicted to be both non-magnetic and metallic, which should promote efficient electron transfer in the anode. Cu$_2$P's favorable properties as a metallic, high capacity material suggest its use as a future conversion anode for Li-ion batteries; with a volume expansion of 99% during complete cycling, Cu$_2$P anodes could be more durable than other conversion anodes in the Cu-P system with volume expansions greater than 150%.
## Description of data
This record contains two entries: `CuP_results.ipynb` and `HarperCuPData.zip`.
- `CuP_results.ipynb` is a Jupyter notebook that contains all of the analysis from the paper. This can also be found on GitHub at https://github.com/harpaf13/data.copper-phosphides and can be explored interactively on Binder https://mybinder.org/v2/gh/haperaf13/data.copper_phosphides/master.
- `HarperCuPData.zip` contains the outputs of all calculations mentioned in the paper. When inflated, it has the following folder structure:
- `Cu2P/`: contains 3 sub-folders `SOC`, `bandstructure` and `phonon` containing calculations on the novel Fm-3m Cu2P phase presented in this paper.
- `Cu2P-Cu3P-phases/`: contains `.res` files for the structures of Cu2P and Cu3P phases discussed in the text.
- `Cu2P-Ir2P-Rh2P-phases/`: contains `.res` files for the structures of Cu2P, Ir2P and Rh2P phases discussed in the text.
- `Cu3P11-Cu2P7-CuP2/`: contains `.res` files for the structures of Cu3P11, Cu2P7 and CuP2 phases discussed in the text.
- `CuPHull/`: contains all `.res` and `.castep` files used to create the convex hull of Cu-P.
- `Ir2P/` and `Rh2P/`: both contain the outputs of spin-orbit corrected bandstructures for Ir2P and Rh2P.
- `PPhonon/`: contains the output of phonon calculations on black phosphorus using the PBE+MBD* and SCAN functionals respectively.
- `TDHull/`: contains the output of PBE phonon calculations performed on all low-lying structures on the Cu-P hull.
- `VoltageCurve/`: contains all output of geometry optimization calculations for all the phases used to construct the voltage curves in the paper.