Computational Modelling

DFT electronic-structure calculations using Dmol3 and CASTEP; PBE and PBE+U

SCU-15 DFT model sample · Model

PBE functional; DSPP for U in Dmol3; CASTEP PBE+U with U = 2.00 eV for U 5f shells, 350.0 eV cutoff, 1e-6 eV/atom SCF tolerance, 0.1 eV smearing, 5 x 3 x 5 Monkhorst-Pack grid.

Geometry: periodic unit cell
Context: SCU-15 model system
Measurement source: main p.4 and p.9 · Density functional theory calculations; Computation methods · Figure S8

Property	Reported value	Normalised value	Uncertainty	Origin and quality	Source
Electronic-structure mechanism	Ligand-to-metal charge transfer (LMCT) mechanism; conduction band edge mostly U f orbitals and valence band mostly sulfur lone-pair electrons plus benzene rings	—	—	Text Qualitative	main p.4 · Density functional theory calculations · Figure S8
DFT band-structure indirect gap shown in Figure S8	indirect 1.67 eV	—	—	Visual Estimate Approximate	SI p.5 · Supplemental Items · Figure S8
PBE+U corrected band gap	2.48 eV	—	—	Text Exact Reported	main p.4 · Density functional theory calculations · Figure S8

X-ray attenuation efficiency calculation using XCOM mass attenuation coefficients

SCU-15 DFT model sample · Model

Calculated attenuation efficiency at 150 keV using T = 1 - exp(-mu_L x); density parameters from Table S3.

Geometry: material-thickness calculation
Context: SCU-15 material calculation
Measurement source: main p.5 and p.10 · Comparison of optoelectronic properties; X-ray attenuation efficiency calculation · Figure 4B; Figure S9; Table S3

Property	Reported value	Normalised value	Uncertainty	Origin and quality	Source
X-ray attenuation comparison	Reduced thickness of uranium-based SCU-15 can achieve the same X-ray absorption as comparison semiconductors	—	—	Text Qualitative	main p.5 · Comparison of optoelectronic properties · Figure 4B; Figure S9
Density parameter for X-ray attenuation calculation	2.120 g cm-3	—	—	SI Table Exact Reported	SI p.11 · Supplemental Items · Table S3

2 measurement groups · 5 results