Nonadiabatic Molecular Dynamics Research Articles

Fully-Integrated Surface Hopping as Quantum Decoherence Correction in Nonadiabatic Dynamics.

In this work, we present a fully integrated surface hopping approach for nonadiabatic molecular dynamics simulations in extended atomistic systems. In lieu of conducting on-the-fly hopping processes in multiple surface hopping realizations, within the neglect of back-reaction approximation, it is possible to conduct a full resummation of the population dynamics for indefinite time with modest computational cost. Our method provides a way to sum up all histories of piece-wise coherent evolution of quantum system altered with the wave function collapses, yielding converged population dynamics without the need for multiple trajectories. The method can also be viewed as a way to represent decoherence correction in nonadiabatic dynamics. The performance of the approach is demonstrated by comparing its performance with that of the standard trajectory surface hopping approaches with and without decoherence correction as applied to a spin-boson Hamiltonian model and an atomistic fullerene example.

Pseudohalide BF4- Doping Suppresses Lattice Anharmonicity and Passivates the Pb-Pb Dimer in Defective CH3NH3PbI3 Perovskites.

Excess electron-induced Pb-Pb dimer formation critically degrades perovskite solar cell performance by converting shallow defects into deep trap states and generating highly localized small polarons that accelerate nonradiative recombination. Using density functional theory and nonadiabatic molecular dynamics, we demonstrate that pseudohalide BF4- doping can passivate such degradation by stabilizing the PbX6 octahedral framework and maintaining delocalized electrons without small polaron formation. This structural stabilization reduces lattice anharmonicity and atomic thermal fluctuations, while enhanced rigidity prevents the large atomic displacements required for dimer formation. The BF4- doping further weakens electron-vibration interaction and decreases nonadiabatic coupling strength, synergistically extending the carrier lifetime by approximately 6 times. Our findings establish pseudohalide doping as an effective strategy to inhibit excess electron-induced degradation through anharmonicity suppression, providing a broadly applicable approach for enhancing perovskite stability.

Photo- and electrocatalytic conversion driven by transition metal-assisted ferroelectric heterojunction.

Photo- and electrocatalytic conversion driven by transition metal-assisted ferroelectric heterojunction.

Modeling Nonradiative Recombination in CsPbI3 and Ge-Doped Perovskites Via Deep Learning with CNN and Transformer Architectures.

Nonradiative electron-hole recombination is a key factor in the performance bottleneck of perovskite optoelectronic devices, and its rate is highly dependent on nonadiabatic (NA) coupling and electron coherence. Traditional first-principles-based NA coupling calculations have the problems of high computational overhead and low efficiency, which limit their wide application in complex systems such as doping regulation. This work adopts a CsPbI3 and Ge-doped system as the research object, combines density functional theory with nonadiabatic molecular dynamics (NAMD), uses Hammes-Schiffer-Tully (HST) and norm-preserving interpolation (NPI) strategies to systematically evaluate four types of NA couplings, and introduces a variety of deep learning models (including four convolutional neural networks and three Transformer structures) to achieve efficient prediction. Among them, the ResNetPlus model achieved the highest average determination coefficient R2 (0.915) in each task and the TSTPlus model performed best in the Transformer class. After embedding the predicted coupling into the NAMD simulation, the nonradiative recombination lifetime obtained is highly consistent with the direct calculation. Further analysis of spatially localized modes and pure decoherence functions revealed that the enhanced localized vibration frequency caused by Ge doping reduced the coherence time from 9.20 to 4.81 fs, accelerating the decoherence process of the system. At the same time, the enhanced localization of the conduction band minimum and valence band maximum charge distribution led to a significant weakening of the NA coupling strength (HST decreased from 0.296 to 0.171 meV; NPI decreased from 0.832 to 0.407 meV), and the synergistic effect of the two effectively delayed nonradiative recombination (HST lifetime increased from 18.96 to 61.44 ns, while NPI lifetime extended from 1.16 to 6.94 ns). This work not only reveals the microscopic regulation mechanism of Ge doping on the nonequilibrium recombination process but also provides theoretical guidance for the construction of efficient and stable perovskite materials and demonstrates the broad application prospects of deep learning in the modeling of complex excited-state processes.

The Dynamic Rashba Effect Does Not Account for the Prolonged Charge Carrier Lifetime in Metal Halide Perovskites.

Rashba spin-orbit splitting in metal halide perovskites has been widely associated with a direct-to-indirect bandgap transition, a mechanism often proposed to suppress nonradiative recombination and extend carrier lifetimes. To critically assess this hypothesis, we developed a nonadiabatic molecular dynamics framework in momentum space that explicitly incorporates spin-orbit coupling and goes beyond harmonic approximation. Using this approach, we investigated electron-hole recombination dynamics in the racemic (rac), S, and R configurations of the chiral 3BrMBA2PbI4 perovskites. The rac structure, which preserves inversion symmetry, exhibits weak Rashba splitting and retains a direct-like bandgap under thermal fluctuations, yielding ∼1 ns recombination times. In contrast, the chiral S and R configurations break inversion symmetry, display pronounced Rashba splitting, and exhibit an indirect bandgap but show only ∼20% slower recombination. These findings indicate that dynamic Rashba spin-orbit splitting alone does not significantly enhance carrier lifetimes, underscoring the importance of atomistic-level understanding of recombination processes in perovskites.

Basis-Discretized Surface Hopping for Auger Processes.

We develop a basis-discretized nonadiabatic molecular dynamics approach that enables large-scale simulations involving millions of states. The approach introduces a density-of-states (DOS) weighted discretization scheme that maps electronic state quasi-continua onto a manageable discrete set, while preserving the original DOS profile, with enhanced resolution near band edges. Benchmarks using both time-dependent Schrödinger equation and fewest-switches surface hopping confirm that the dynamics remain consistent before and after the discretization. The method is applied to study Auger-type processes in a silicon quantum dot by reducing an otherwise intractable basis set to a manageable discretized model. The simulations show that biexciton and triexciton states significantly broaden energy dissipation pathways and accelerate electron-vibrational energy relaxation via Coulomb-mediated Auger processes, as compared to the single exciton dynamics. The work offers an efficient and robust framework for accurate simulations of excited-state dynamics in low-dimensional and nanoscale materials at the atomistic level.

Asymmetric Spin Relaxation Dynamics of Electrons and Holes in CsPbI3: An Ab Initio Quantum Dynamics Study.

Lead halide perovskites are promising for spintronics due to their strong spin-orbit coupling (SOC). Experiments show asymmetric, temperature-dependent spin relaxation in γ-CsPbI3, with electrons relaxing faster than holes via the Elliott-Yafet carrier-phonon mechanism. Ab initio non-adiabatic molecular dynamics with SOC and half-electron correction reproduce this asymmetry. The difference arises from band-edge orbital character: the conduction band minimum (CBM) is Pb-p-dominated and spin-mixed under SOC, while the valence band maximum remains spin-pure due to s-type Pb and I p orbitals. Spin mixing in the CBM leads to a smaller spin mismatch and stronger non-adiabatic couplings, accelerating electron spin relaxation. Lower temperatures extend spin lifetimes by reducing carrier-phonon interactions. In contrast, elevated temperatures enhance lattice disorder and spin state mixing, increasing wave function overlap and non-adiabatic couplings, thereby speeding up spin relaxation. This work offers atomistic insight into asymmetric and temperature-dependent spin dynamics, influencing spintronic device design through thermal and structural control.

Efficient Z-Scheme Photocatalyst for Hydrogen Production via Water Splitting Using CH3- and F-Modified C60 Fullerene-Based Heterostructures.

The ability to drive overall water splitting and efficiently utilize carriers is critical for optimizing photocatalytic performance to promote hydrogen production. Modifying photocatalysts with functional groups such as F and CH3 can significantly enhance these capabilities. Our results show that the large electrostatic potential at the surfaces of CH3@C60/ZrS2, F@qHP-C60/GeC, and F@qHP-C60/Bi heterostructures not only improves carrier separation but also increases the overpotentials for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Moreover, the Gibbs free energies (ΔG) for HER and OER are notably reduced, due to a more localized charge density distribution that facilitates the spontaneous occurrence of these reactions. Non-adiabatic molecular dynamics simulations demonstrate that the smaller band gaps in these CH3 and F-modified C60-based heterostructures can result in faster electron-hole (e-h) recombination and enhanced carrier lifetime. These improvements contribute to a more efficient Z-scheme and superior carrier separation. In short, compared to the unmodified structures, the incorporation of radicals enhances the ability to drive HER and OER spontaneously, reduces ΔG, strengthens thermodynamic stability, accelerates e-h recombination, and increases the visible light absorption coefficient; all of the above contribute to the possibility of heterostructures becoming promising photocatalysts. This work introduces novel high-performance photocatalysts and offers valuable insights for developing efficient photocatalysts based on C60 and qHP-C60 monolayers.

Photocatalysis at the Molecule/Metal Oxide Interface Is Driven by Asymmetric Photocarrier Transfer: Ab Initio Quantum Dynamics Simulation.

The photocatalytic efficiency of a molecule/metal oxide interface critically depends on the dynamic competition between forward carrier transfer to the molecule and reverse transfer to the substrate. Using CH3O-/TiO2 as a prototypical system and employing nonadiabatic molecular dynamics simulations with hybrid density functional theory, we reveal the complete cascade of atomistic processes following photoexcitation. Our results demonstrate that accurately predicting carrier dynamics in photocatalysis requires a comprehensive understanding of the full photochemical sequence involves carrier trapping, post-trapping stabilization, and subsequent dissociation. In the trapping process, despite an unfavorable 0.55 eV HOMO-VBM offset under static conditions that would suggest minimal hole trapping, thermal fluctuations dynamically modulate adsorbate-substrate hybridization, enabling transient photogenerated hole capture. Critically, when trapped hole stabilization occurs via CH3O· radical formation, the reverse transfer time scale dramatically extends from sub-10 fs to sub-10 ps, a rise of 3 orders of magnitude. This radical state elevates the trap-state energy, suppressing reverse transfer and extending carrier lifetimes sufficiently to enable subsequent chemistry. The metastable radical further reduces the C-H dissociation barrier, driving spontaneous photodecomposition via proton-coupled charge transfer. Our findings reconcile long-standing theory-experiment discrepancies by demonstrating that a dual energy alignment framework in the molecule/metal oxide interface: initial charge capture requires pretrapping energy matching, while post-trapping stabilization via chemical intermediates creates an energetic asymmetry that effectively suppresses carrier dissipation. This mechanistic understanding of interfacial charge dynamics provides fundamental design principles for the rational development of high-efficiency photocatalytic systems.

Defect inducing large spin orbital coupling enhances magnetic recovery dynamics in CrI3 monolayer

The rapid magnetic recovery process (MRP) after photoexcitation is crucial for efficient information recording in magnets but is often impeded by insufficient spin flip channels. Using time-domain ab initio nonadiabatic molecular dynamics including spin-orbital coupling (SOC), we investigate MRP in a CrI3 ferromagnetic monolayer and find that defects can accelerate this process. In defect-free CrI3, MRP is slow (400 fs) due to weak SOC between spin-majority and spin-minority valence band edges, notably limiting spin flips during relaxation. Intrinsic vacancy defects (VI and VCr), particularly the VCr defect, disrupt the system’s rotational symmetry by extending their states asymmetrically to bulk I ions. The lowered symmetry significantly enhances SOC near the valence band edges and speeds up MRP to 100 fs by promoting spin flips. This study uncovers the origins of slow MRP in CrI3 monolayer and highlights defect engineering as a promising strategy to improve MRP for optically excited spintronic devices.

Machine Learning-Driven Band Alignment Strategy for Screening 1T-TMDs-Based Z-Scheme Heterostructures toward Efficient Photocatalytic Water Splitting.

To address the global energy crisis and mitigate environmental challenges stemming from fossil fuel dependence, advancing efficient photocatalytic water splitting technology has become a critical focus in renewable energy research. An innovative design strategy for high-efficiency photocatalysts based on band edge alignment is established through the integration of machine learning (ML) and first-principles computational methods, developing a high-throughput screening framework specifically targeting 1T-phase transition metal dichalcogenides (1T-TMDs). Through optimized feature selection, ML models, and training protocols, the PdSSe monolayer is identified as exhibiting ideal band edge compatibility with the GeC monolayer. Subsequent density functional theory (DFT) verification confirmed exceptional agreement with ML predictions. The GeC/SPdSe Z-scheme heterostructure achieves remarkable photocatalytic efficiency, driven by its optimally aligned band structure that enables spontaneous hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) under visible-light irradiation. Nonadiabatic molecular dynamics (NAMD) simulations reveal that photo-generated carriers in heterostructures follow a Z-scheme pathway, as supported by distinct timescales of electron-hole migration and recombination. This heterostructure architecture exhibits broadband light absorption spanning the visible to ultraviolet spectral regions, yielding a remarkable theoretical solar-to-hydrogen (STH) efficiency of 29.5%.

Sulfur Passivation Engineering of Carbon Defects in N-Surface GaN: Suppressing Nonadiabatic Carrier Recombination Via Self-Compensated SN-CN Complexes.

In gallium nitride (GaN), the carbon-on-nitrogen substitutional defect (CN) has been extensively investigated as a prototypical deep acceptor center, particularly for its well-characterized yellow luminescence associated with the (-/0) transition. However, the carrier dynamics involving its secondary (0/+) transition remains poorly understood. Combining first-principles calculations and nonadiabatic molecular dynamics simulations, we systematically investigate the nonradiative carrier capture processes mediated by the CN defects on nitrogen-terminated GaN surfaces, along with their sulfur-based passivation mechanisms. Our results demonstrate that the neutral CN defect serves as a critical nonradiative recombination center, exhibiting an ultrafast hole capture rate (τ ≈ 10-12 s). Notably, sulfur atoms can migrate with a low energy barrier (0.64 eV) to occupy adjacent nitrogen vacancies on the N surface, forming SN-CN complex defects through a self-compensation mechanism. This structural modification induces a significant charge redistribution, shifting the defect level from deep within the bandgap to near the valence band maximum. Such electronic structure modulation effectively suppresses nonadiabatic transitions between defect states and the valence band. This work provides the first atomistic visualization of sulfur passivation mechanisms for CN defects in GaN, establishing a quantitative relationship between defect configuration engineering and carrier recombination dynamics.

Theoretical Insight into the Oxyacid Anions Boost Tin‐Based Perovskite Toward the Oxygen Contamination Avoidance and Charge Carrier Lifetime Extension

Abstract Tin (Sn)‐based perovskite solar cells (PSCs) stand out as a promising low‐toxicity alternative to lead (Pb)‐based PSCs. However, their progress is hindered by oxygen‐induced degradation and inherent crystal defects, challenging their efficiency and durability. Through density functional theory (DFT) calculations, it is found that oxyacid anions including HCOO−, HSO3−, and H2PO2− can strongly coordinate with the SnI2 precursor to form adducts. These complexes help inhibit Sn2+/Sn4+ oxidation in the precursor solution, slow down the crystallization process, and ultimately improve the crystal quality of CsSnI3. Moreover, these oxyacid anions bind to the iodine vacancies (IV) and alloy within the crystal lattice, thereby preventing oxygen molecules from generating detrimental superoxide ions at these sites. Electron structure analysis and nonadiabatic molecular dynamics (NAMD) simulations show that these anions not only eliminate trap states by disrupting the 5p‐5p orbitals interaction of Sn atoms near IV, but also reduce the oscillation of key energy states and weaken nonadiabatic coupling (NAC). These effects collectively contribute to the extended lifetime of charge carriers. Notably, the charge carrier lifetime in the system passivated with H2PO2− is extended by more than 15 times. Consequently, the oxyacid anions are seen to synergistically enhance the performance of Sn‐based PSCs.

Tipping the ultrafast photochemical balance of cis-stilbene.

Multi-state nonadiabatic molecular dynamics simulations combined with MRSF-TDDFT have revealed that the quantum yield of photoproducts in cis-stilbene is dependent on the initial temperature of the ground state, thereby resolving controversies regarding the competition between isomerization and ring-closure reactions. Specifically, 4,4-dihydrophenanthrene (DHP) is preferentially formed at low temperatures, while trans-stilbene is favored at high temperatures. The ethylenic torsional motions ( ) are particularly coupled with the initial thermal condition, tipping the balance of the competition.

Theoretical Insights into Ultrafast-Decaying and Long-Lived States of ortho-Nitrophenol upon Photoexcitation in the Gas Phase.

Nitrophenols in the atmosphere are chromophore pollutants that absorb sunlight. Among them, ortho-nitrophenol (o-NP) stands out due to its strong intramolecular hydrogen bond which facilitates excited-state intramolecular proton transfer (ESIPT) and influences its photoisomerization and dissociation. Time-resolved experiments have captured both ultrafast-decaying and long-lived signals. Here, we employ non-adiabatic molecular dynamics simulations and the reaction space projector method to elucidate the photoinduced reactions of o-NP. Our simulations show that photoexcited o-NP in the S1(ππ*) state undergoes ultrafast ESIPT followed by rapid decay through one of two non-adiabatic pathways: ultrafast internal conversion to the S0 state and intersystem crossing (ISC) to the triplet states. Furthermore, trajectories undergoing ISC remain trapped in triplet states, with reverse ISC to the singlet states rarely observed. These trajectories are clearly linked to the long-lived excited-state signal, providing more conclusive computational evidence of the origin.

Ultrafast Bright-to-Dark Exciton Relaxation in Bilayer Borophene Driven by Strong Excitonic Effects.

Exciton dynamics in the recently discovered bilayer borophene (BL-α5, consisting of two stacked v1/12 boron sheets) are of great interest due to this material's promising electronic and optical properties for nano-optoelectronic applications. Using a GW plus real-time Bethe-Salpeter equation (GW-rtBSE) approach and ab initio nonadiabatic molecular dynamics (NAMD), we identify a Frenkel-type lowest-energy bright exciton and a spatially delocalized dark exciton in BL-α5, with large binding energies of ∼700 and ∼502 meV, respectively. The electron-hole (e-h) Coulomb interaction (exciton effect) dominates over electron-phonon (e-ph) scattering, playing a pivotal role in an ultrafast bright-to-dark exciton transition with a relaxation time of ∼150 fs. Furthermore, the dark excitons undergo nonradiative recombination on a picosecond time scale (∼14 ps at room temperature). These results provide a theoretical foundation for potential nano-optoelectronic and light-energy harvesting applications of bilayer borophene.

Ultrafast charge transfer in two-dimensional black phosphorus/SiS van der Waals heterostructure for photoconversion

The construction of two-dimensional (2D) van der Waals (vdW) heterostructures is a promising strategy for developing advanced optoelectronic and photovoltaic devices. In this work, we first construct a 2D van der Waals heterostructure composed of black phosphorus (BP) and Pma2-SiS with type-II band alignment. Then, we employ ab initio nonadiabatic molecular dynamics based on the HSE06 hybrid functional to investigate its interfacial charge transfer dynamics. Our computational results reveal that the ultrafast hole transfer takes within 156 fs, whereas the electron transfer is suppressed greatly. Further analysis reveals that the ultrafast hole transfer process is driven by two key factors: the availability of sufficient hole transfer pathways at the interface to effectively accept the photoexcited holes, and the strong electron–phonon coupling originating from the interlayer shear mode along the zigzag direction as well as the optical phonon modes of BP. These findings provide valuable insights into the charge transfer dynamics in 2D vdW heterostructures and guide the design of high-performance optoelectronic and photovoltaic devices.

Unidirectional molecular rotary motor with remotely switchable rotation direction.

Light-driven rotary motors allow direct transformation of light energy into rotary motion at the nanoscale, giving rise to countless emerging applications in molecular engineering. The key feature enabling the unidirectional rotation and controlling its direction is the motor chirality, a factor hard to modify postsynthetically. Here, we propose a motor architecture, E-motor, whose operation direction can be switched remotely with an electric field pulse, without the need for chemical intervention. Our study relies on quantum chemical calculations and nonadiabatic molecular dynamics simulations performed for a specifically tailored system, PFCN, designed to provide illustration for the proposed motor type. We show that the PFCN chirality depends on the orientation of a covalently bound polar switching unit, which can be controlled with the electric field. At the same time, the proposed system manifests all characteristic photophysical properties of a molecular motor, and its set chirality is preserved during operation in the absence of the field.

Elucidating the effects of isoelectronic atomic substitution on the excited-state dynamics and reactivity of aromatic compounds.

Photochemistry of aromatic compounds has attracted significant interest for their distinctive excited-state behavior and potential applications as energy materials. Isoelectronic atomic substitution, which involves replacing ring atoms while maintaining the same number of electrons in aromatic compounds (e.g., from C-C to B-N), offers a promising strategy for modulating these properties by tuning electronic structures. However, a fundamental understanding of its effect on the excited-state dynamics and reactivity remains elusive. In this study, we investigate the photochemical properties of oxaborine, using benzene and azaborine as references, to elucidate the effects of isoelectronic atomic substitution. Potential energy surface (PES) calculations reveal that oxaborine undergoes barrierless ring distortion toward S1/S0 conical intersection (CI), followed by barrierless Dewar isomerization directly from the S1/S0 CI. Using nonadiabatic molecular dynamics simulations, we observe a rapid S1 decay time (125fs) and a notably high Dewar isomerization yield (23.3%), consistent with the results of PES calculations, highlighting the unique photochemical properties of oxaborine. Orbital-level analysis reveals that atomic substitution breaks the π orbital degeneracy and destabilizes the S1 state, explaining the much faster S1 decay for azaborine and oxaborine. The p orbital energy modulations from O-B or N-B substitution weaken the meta-bridge bond while enhancing para-bridge C-C interactions, favoring Dewar isomerization. These findings offer a comprehensive understanding of the effect of isoelectronic atomic substitution in aromatic compounds and demonstrate its potential as a design strategy for controlling photochemical properties.

Energy Transfer Mechanisms in Large Low-Bandgap Polymers from Time-Resolved Experiments and Nonadiabatic Molecular Dynamics Calculations.

Conjugated polymers offer unprecedented chemical tunability for modulating energy transfer in a multitude of infrared light applications. In this work, we use a combination of time-resolved spectroscopic experiments and nonadiabatic molecular dynamics calculations to probe the photochemistry and nonradiative transitions in a recently synthesized narrow bandgap donor-acceptor conjugated polymer based on alternating cyclopentadithiophene and electronegative benzothiadiazole heterocycles. Using large-scale semi-empirical nonadiabatic molecular dynamics, which can treat a large 260-atom hexamer, we calculate an S5 → S1 lifetime of 34.75 fs, which is consistent with our time-resolved spectroscopic data. Our simulations suggest that vibronic motions of the central carbons in the cyclopentadithiophene functional groups are predominantly involved in the nonradiative transitions, and the excitation becomes more localized on a monomer fragment over time. The combined use of time-resolved experiments and nonadiabatic molecular dynamics calculations in this work provides mechanistic insight into chemical functionalities that can be tuned to enhance energy transfer in other prospective low-bandgap polymer materials.