Integrated xTB and simplified Tamm–Dancoff analysis of composition-dependent electronic structure in GaInZnP/ZnSeyS1-y core/shell quantum dots with DFT and TDDFPT benchmarking

TY - JOUR

T1 - Integrated xTB and simplified Tamm–Dancoff analysis of composition-dependent electronic structure in GaInZnP/ZnSeyS1-y core/shell quantum dots with DFT and TDDFPT benchmarking

AU - Adegoke, Oluwasesan

AU - Achadu, Ojodomo J.

N1 - Publisher Copyright: © The Author(s) 2026.

PY - 2026/5/8

Y1 - 2026/5/8

N2 - Context: Alloyed core/shell quantum dots (QDs) provide a platform for composition-controlled modulation of electronic structure and optical response. Using an integrated extended tight binding (xTB) and simplified Tamm Dancoff approximation (sTDA) framework, a composition-defined GaInZnP/ZnSe yS 1-y core/shell QD series (y = 0.00, 0.25, 0.50, 0.75, 1.00) revealed a distinctly nonlinear dependence of electronic and excited-state behaviour on shell composition. Relative stability favoured S-rich shells, while mixed-shell compositions showed non-ideal energetic behaviour with a pronounced deviation at y = 0.75. The frontier electronic structure did not vary monotonically with Se content, while the optical response showed composition-dependent redistribution of low-energy transitions. Benchmark comparison with density functional theory (DFT) and time-dependent density functional perturbation theory (TDDFPT) confirmed that the nonlinear evolution of frontier-level separation and absorption behaviour was an intrinsic feature of the alloy series, although the exact magnitude and position of the extrema remain method dependent. A distinct anomaly at y = 0.75 indicated enhanced frontier state reorganisation within the mixed-shell environment. Method: Atomistic GaInZnP/ZnSe yS 1-y QDs spanning y = 0.00 to 1.00 were analysed under identical structural constraints to isolate shell anion substitution effects. Ground-state electronic structure and excited-state properties were evaluated using xTB and sTDA, with DFT and TDDFPT used as independent benchmarks for frontier electronic structure and optical absorption trends. Composition-dependent changes in energetic stability, frontier-orbital separation, density-of-states like distributions, absorption onset, and frontier-orbital localisation were then compared across the full alloy series using a consistent analysis framework.

AB - Context: Alloyed core/shell quantum dots (QDs) provide a platform for composition-controlled modulation of electronic structure and optical response. Using an integrated extended tight binding (xTB) and simplified Tamm Dancoff approximation (sTDA) framework, a composition-defined GaInZnP/ZnSe yS 1-y core/shell QD series (y = 0.00, 0.25, 0.50, 0.75, 1.00) revealed a distinctly nonlinear dependence of electronic and excited-state behaviour on shell composition. Relative stability favoured S-rich shells, while mixed-shell compositions showed non-ideal energetic behaviour with a pronounced deviation at y = 0.75. The frontier electronic structure did not vary monotonically with Se content, while the optical response showed composition-dependent redistribution of low-energy transitions. Benchmark comparison with density functional theory (DFT) and time-dependent density functional perturbation theory (TDDFPT) confirmed that the nonlinear evolution of frontier-level separation and absorption behaviour was an intrinsic feature of the alloy series, although the exact magnitude and position of the extrema remain method dependent. A distinct anomaly at y = 0.75 indicated enhanced frontier state reorganisation within the mixed-shell environment. Method: Atomistic GaInZnP/ZnSe yS 1-y QDs spanning y = 0.00 to 1.00 were analysed under identical structural constraints to isolate shell anion substitution effects. Ground-state electronic structure and excited-state properties were evaluated using xTB and sTDA, with DFT and TDDFPT used as independent benchmarks for frontier electronic structure and optical absorption trends. Composition-dependent changes in energetic stability, frontier-orbital separation, density-of-states like distributions, absorption onset, and frontier-orbital localisation were then compared across the full alloy series using a consistent analysis framework.

KW - Electronic structure

KW - DFT

KW - TDDFPT

KW - Quantum dots

KW - xTD

KW - sTDA

U2 - 10.1007/s00894-026-06728-1

DO - 10.1007/s00894-026-06728-1

M3 - Article

SN - 1610-2940

VL - 32

JO - Journal of Molecular Modeling

JF - Journal of Molecular Modeling

M1 - 172

ER -