Generating High-Precision Force Fields for Molecular Dynamics Simulations to Study Chemical Reaction Mechanisms Using Molecular Configuration Transformer.

Theoretical studies on chemical reaction mechanisms have been crucial in organic chemistry. Traditionally, calculating the manually constructed molecular conformations of transition states for chemical reactions using quantum chemical calculations is the most commonly used method. However, this way is heavily dependent on individual experience and chemical intuition. In our previous study, we proposed a research paradigm that used enhanced sampling in molecular dynamics simulations to study chemical reactions. This approach can directly simulate the entire process of a chemical reaction. However, the computational speed limited the use of high-precision potential energy functions for simulations. To address this issue, we presented a scheme for training high-precision force fields for molecular modeling using a previously developed graph-neural-network-based molecular model, molecular configuration transformer. This potential energy function allowed for highly accurate simulations at a low computational cost, leading to more precise calculations of the mechanism of chemical reactions. We applied this approach to study a Claisen rearrangement reaction and a carbonyl insertion reaction catalyzed by manganese.

Quantum Uncertainty Principles for Measurements with Interventions.

Heisenberg's uncertainty principle implies fundamental constraints on what properties of a quantum system we can simultaneously learn. However, it typically assumes that we probe these properties via measurements at a single point in time. In contrast, inferring causal dependencies in complex processes often requires interactive experimentation-multiple rounds of interventions where we adaptively probe the process with different inputs to observe how they affect outputs. Here, we demonstrate universal uncertainty principles for general interactive measurements involving arbitrary rounds of interventions. As a case study, we show that they imply an uncertainty trade-off between measurements compatible with different causal dependencies.

An Interpretable Time Series Data Prediction Framework for Severe Accidents in Nuclear Power Plants.

Accurately predicting severe accident data in nuclear power plants is of utmost importance for ensuring their safety and reliability. However, existing methods often lack interpretability, thereby limiting their utility in decision making. In this paper, we present an interpretable framework, called GRUS, for forecasting severe accident data in nuclear power plants. Our approach combines the GRU model with SHAP analysis, enabling accurate predictions and offering valuable insights into the underlying mechanisms. To begin, we preprocess the data and extract temporal features. Subsequently, we employ the GRU model to generate preliminary predictions. To enhance the interpretability of our framework, we leverage SHAP analysis to assess the contributions of different features and develop a deeper understanding of their impact on the predictions. Finally, we retrain the GRU model using the selected dataset. Through extensive experimentation utilizing breach data from MSLB accidents and LOCAs, we demonstrate the superior performance of our GRUS framework compared to the mainstream GRU, LSTM, and ARIMAX models. Our framework effectively forecasts trends in core parameters during severe accidents, thereby bolstering decision-making capabilities and enabling more effective emergency response strategies in nuclear power plants.

BDF: A relativistic electronic structure program package.

The BDF (Beijing Density Functional) program package is in the first place a platform for theoretical and methodological developments, standing out particularly in relativistic quantum chemical methods for chemistry and physics of atoms, molecules, and periodic solids containing heavy elements. These include the whole spectrum of relativistic Hamiltonians and their combinations with density functional theory for the electronic structure of ground states as well as time-dependent and static density functional linear response theories for electronically excited states and electric/magnetic properties. However, not to be confused by its name, BDF nowadays comprises also of standard and novel wave function-based correlation methods for the ground and excited states of strongly correlated systems of electrons [e.g., multireference configuration interaction, static-dynamic-static configuration interaction, static-dynamic-static second-order perturbation theory, n-electron valence second-order perturbation theory, iterative configuration interaction (iCI), iCI with selection plus PT2, and equation-of-motion coupled-cluster]. Additional features of BDF include a maximum occupation method for finding excited states of Hartree-Fock/Kohn-Sham (HF/KS) equations, a very efficient localization of HF/KS and complete active space self-consistent field orbitals, and a unique solver for exterior and interior roots of large matrix eigenvalue problems.

Hydration-Facilitated Fine-Tuning of the AIE Amphiphile Color and Application as Erasable Materials with Hot/Cold Dual Writing Modes.

Hydration water greatly impacts the color of inorganic crystals, but it is still unknown whether hydration water can be utilized to systematically manipulate the emission color of organic luminescent groups. Now, metal ions with different hydration ability allow fine-tuning the emission color of a fluorescent group displaying aggregation induced emission (AIE). Because the hydration water can be removed easily by gentle heating or mechanical grinding and re-gained by solvent fuming, rewritable materials can be fabricated both in the hot-writing and cold-writing modes. This hydration-facilitated strategy will open up a new vista in fine-tuning the emission color of AIE molecules based on one synthesis and in the design of smart luminescent devices.

Sublinear scaling quantum chemical methods for magnetic shieldings in large molecules.

It is shown that quantum chemical calculations of the nuclear magnetic shieldings of a group of vicinal nuclei in a large molecule can be made sublinear scaling [i.e., O(1)] with respect to the molecular size. This is achieved by making both the diamagnetic and paramagnetic terms translation invariant [following the work of Ochsenfeld et al. J. Chem. Phys. 134, 074102 (2011)] and by making use of a local representation that is independent of the molecular size. Although only Hartree-Fock results are reported here, the idea can readily be extended to correlated wave function methods as well as the relativistic domain.

Relativistic time-dependent density functional theories.

The foundations, formalisms, technicalities, and practicalities of relativistic time-dependent density functional theories (R-TD-DFT) for spinor excited states of molecular systems containing heavy elements are critically reviewed. These include the four-component (4C) and exact two-component (X2C) variants (4C/X2C-TD-DFT) that treat both scalar relativistic effects and spin-orbit couplings (SOC) to infinite order, and a composite two-component variant (sf-X2C-S-TD-DFT-SOC) that treats scalar relativistic effects to infinite order via the spin-free part of the X2C Hamiltonian (sf-X2C) but SOC to first order via the Douglas-Kroll-Hess type of spin-orbit operator resulting also from the spin separation of the X2C Hamiltonian. Except for the common adiabatic approximation, the most essential ingredient for all the three variants of R-TD-DFT is the noncollinear exchange-correlation kernel that is invariant with respect to rotations in spin space. It is unfortunate that 4C- and X2C-TD-DFT cannot be made fully symmetry adapted for open-shell systems except for some special cases. Yet, this is possible for closed-shell systems by working with both double point group and time reversal adapted molecular spinors. In particular, the spinor Hessian can be made real-valued in this case, such that the 4C/X2C-TD-DFT eigenvalue problems can be solved in the same manner as nonrelativistic TD-DFT, a point that is discovered here for the first time. By contrast, sf-X2C-S-TD-DFT-SOC can access spinor excited states of both closed- and open-shell systems because spin symmetry is fully accounted for in the spin-adapted TD-DFT (S-TD-DFT). Possible further developments of R-TD-DFT are also highlighted.

Allosteric Self-Assembly of Coordinating Terthiophene Amphiphile for Triggered Light Harvesting.

Allosteric regulation is extensively employed by nature to achieve functional control of protein or deoxyribonucleic acid through triggered conformational change at a remote site. We report that a similar strategy can be utilized in artificial self-assembly to control the self-assembled structure and its function. We show that on binding of metal ions to the headgroup of an amphiphile TTC4L, the conformational change may lead to change of the dipole orientation of the energy donor at the chain end. This on the one hand leads to a drastically different self-assembled structure; on the other hand, it enables light harvesting between the donor-acceptor. Because the Forster resonance fluorescence transfer efficiency is gated by metal ions, controlling the feeding of metal ions allows switching on and off of light harvesting. We expect that using allosteric self-assembly, we will be able to create abundant structures with distinct function from limited molecules, which show prominent potential for the postorganic modification of the structure and function of self-assembled materials.

iVI: An iterative vector interaction method for large eigenvalue problems.

Based on the generic "static-dynamic-static" framework for strongly coupled basis vectors (Liu and Hoffman, Theor. Chem. Acc. 2014, 133, 1481), an iterative Vector Interaction (iVI) method is proposed for computing multiple exterior or interior eigenpairs of large symmetric/Hermitian matrices. Although it works with a fixed-dimensional search subspace, iVI can converge quickly and monotonically from above to the exact exterior/interior roots. The efficacy of iVI is demonstrated by taking both mathematical and physical matrices as examples. © 2017 Wiley Periodicals, Inc.

Exact two-component relativistic energy band theory and application.

An exact two-component (X2C) relativistic density functional theory in terms of atom-centered basis functions is proposed for relativistic calculations of band structures and structural properties of periodic systems containing heavy elements. Due to finite radial extensions of the local basis functions, the periodic calculation is very much the same as a molecular calculation, except only for an Ewald summation for the Coulomb potential of fluctuating periodic monopoles. For comparison, the nonrelativistic and spin-free X2C counterparts are also implemented in parallel. As a first and pilot application, the band gaps, lattice constants, cohesive energies, and bulk moduli of AgX (X = Cl, Br, I) are calculated to compare with other theoretical results.

Temperature dependent coordinating self-assembly.

Self-assemblies dominated by coordination interaction are hardly responsive to thermal stimuli. We show that in case the coordinating mode changes with temperature, the resultant assemblies also exhibit temperature dependence. The self-assemblies are constructed with perylene tetracarboxylate and metal ions. Compounds containing a perylene skeleton often self-assemble into micro-belts, which is also true for the combination of perylene tetracarboxylate and metal ions. However, a unique pinecone structure was observed upon increasing the temperature of the coordinating system. The structural transition is triggered by the change of coordinating mode between the carboxylate group and the metal ion. At low temperature, intermolecular coordination occurs which favours the growth of the coordinating self-assembly along the long axis of the perylene. However, upon the elevation of temperature, the coordination is overwhelmed by intra-molecular mode. This is against the extension of the coordinating assembly due to the loss of connection between neighbouring perylenes. As a result, the pinecone structure is observed. We expect that the cases introduced in this work may inspire the design of structurally controllable temperature-dependent soft materials based on coordinating self-assembly.

Relativistic theory of nuclear spin-rotation tensor with kinetically balanced rotational London orbitals.

Both kinetically balanced (KB) and kinetically unbalanced (KU) rotational London orbitals (RLO) are proposed to resolve the slow basis set convergence in relativistic calculations of nuclear spin-rotation (NSR) coupling tensors of molecules containing heavy elements [Y. Xiao and W. Liu, J. Chem. Phys. 138, 134104 (2013)]. While they perform rather similarly, the KB-RLO Ansatz is clearly preferred as it ensures the correct nonrelativistic limit even with a finite basis. Moreover, it gives rise to the same "direct relativistic mapping" between nuclear magnetic resonance shielding and NSR coupling tensors as that without using the London orbitals [Y. Xiao, Y. Zhang, and W. Liu, J. Chem. Theory Comput. 10, 600 (2014)].

On the spin separation of algebraic two-component relativistic Hamiltonians: molecular properties.

The idea for separating the algebraic exact two-component (X2C) relativistic Hamiltonians into spin-free (sf) and spin-dependent terms [Z. Li, Y. Xiao, and W. Liu, J. Chem. Phys. 137, 154114 (2012)] is extended to both electric and magnetic molecular properties. Taking the spin-free terms (which are correct to infinite order in α ≈ 1/137) as zeroth order, the spin-dependent terms can be treated to any desired order via analytic derivative technique. This is further facilitated by unified Sylvester equations for the response of the decoupling and renormalization matrices to single or multiple perturbations. For practical purposes, explicit expressions of order α(2) in spin are also given for electric and magnetic properties, as well as two-electron spin-orbit couplings. At this order, the response of the decoupling and renormalization matrices is not required, such that the expressions are very compact and completely parallel to those based on the Breit-Pauli (BP) Hamiltonian. However, the former employ sf-X2C wave functions, whereas the latter can only use nonrelativistic wave functions. As the sf-X2C terms can readily be interfaced with any nonrelativistic program, the implementation of the O(α²) spin-orbit corrections to sf-X2C properties requires only marginal revisions of the routines for evaluating the BP type of corrections.

Highly efficient ion-transport "polymer-in-ceramic" electrolytes boost stable all-solid-state Li metal batteries.

"Polymer-in-ceramic" (PIC) electrolytes are widely investigated for all-solid-state batteries (ASSBs) due to their good thermal stability and mechanical performance. However, achieving fast and diversified lithium-ion transport inside the PIC electrolyte and uniform Li+ deposition at the electrolyte/Li anode interface simultaneously remains a challenge. Besides, the effect of ceramic particle size on Li+ transport and Li anodic compatibility is still unclear, which is essential for revealing the enhanced mechanism of the performance for PIC electrolytes. Herein, PIC with moderate ceramic size and contents are prepared and studied to strike a balance between ionic conductivity and anodic compatibility. Through moderate filler-filler interfacial impedance and appropriate surface roughness, a particle size of 17 µm is optimized to facilitate homogeneous Li+ flux on anode and enhance Li+ conductivity of the electrolyte. The PIC electrolyte with ceramic particle size of 17 µm achieves a high lithium ion transference number (0.74) and an ionic conductivity of 4.11 × 10-4 S cm-1 at 60 °C. The Li/PIC/Li symmetric cell can stably cycle for 2800 h at 0.2 mA cm-2 with 0.2 mAh cm-2. Additionally, the Li/PIC/LiFePO4 cell also delivers a superior cycling performance at 0.5C, a high capacity retention of 93.28% after 100 cycles and 83.17% after 200 cycles, respectively.

Room-Temperature Band-Aligned Infrared Heterostructures for Integrable Sensing and Communication.

The demand for miniaturized and integrated multifunctional devices drives the progression of high-performance infrared photodetectors for diverse applications, including remote sensing, air defense, and communications, among others. Nonetheless, infrared photodetectors that rely solely on single low-dimensional materials often face challenges due to the limited absorption cross-section and suboptimal carrier mobility, which can impair sensitivity and prolong response times. Here, through experimental validation is demonstrated, precise control over energy band alignment in a type-II van der Waals heterojunction, comprising vertically stacked 2D Ta2NiSe5 and the topological insulator Bi2Se3, where the configuration enables polarization-sensitive, wide-spectral-range photodetection. Experimental evaluations at room temperature reveal that the device exhibits a self-powered responsivity of 0.48 A·W-1, a specific directivity of 3.8 × 1011 cm·Hz1/2·W-1, a response time of 151 µs, and a polarization ratio of 2.83. The stable and rapid photoresponse of the device underpins the utility in infrared-coded communication and dual-channel imaging, showing the substantial potential of the detector. These findings articulate a systematic approach to developing miniaturized, multifunctional room-temperature infrared detectors with superior performance metrics and enhanced capabilities for multi-information acquisition.

Radiotherapy-triggered reduction of platinum-based chemotherapeutic prodrugs in tumours.

Pt(II) drugs are a widely used chemotherapeutic, yet their side effects can be severe. Here we show that the radiation-induced reduction of Pt(IV) complexes to cytotoxic Pt(II) drugs is rapid, efficient and applicable in water, that it is mediated by hydrated electrons from water radiolysis and that the X-ray-induced release of Pt(II) drugs from an oxaliplatin prodrug in tumours inhibits their growth, as we show with nearly complete tumour regression in mice with subcutaneous human tumour xenografts. The combination of low-dose radiotherapy with a Pt(IV)-based antibody-trastuzumab conjugate led to the tumour-selective release of the chemotherapeutic in mice and to substantial therapeutic benefits. The radiation-induced local reduction of platinum prodrugs in the reductive tumour microenvironment may expand the utility of radiotherapy.

Body-fixed relativistic molecular Hamiltonian and its application to nuclear spin-rotation tensor.

A relativistic molecular Hamiltonian that describes electrons fully relativistically and nuclei quasi-relativistically is proposed and transformed from the laboratory to the body-fixed frame of reference. As a first application of the resulting body-fixed relativistic molecular Hamiltonian, the long anticipated relativistic theory of nuclear spin-rotation (NSR) tensor is formulated rigorously. A "relativistic mapping" between experimental NSR and NMR is further proposed, which is of great value in establishing high-precision absolute NMR shielding scales.

Body-fixed relativistic molecular Hamiltonian and its application to nuclear spin-rotation tensor: linear molecules.

The relativistic molecular Hamiltonian written in the body-fixed frame of reference is the basis for high-precision calculations of spectroscopic parameters involving nuclear vibrations and/or rotations. Such a Hamiltonian that describes electrons fully relativistically and nuclei quasi-relativistically is just developed for semi-rigid nonlinear molecules [Y. Xiao and W. Liu, J. Chem. Phys. 138, 134104 (2013)]. Yet, the formulation should somewhat be revised for linear molecules thanks to some unusual features arising from the redundancy of the rotation around the molecular axis. Nonetheless, the resulting isomorphic Hamiltonian is rather similar to that for nonlinear molecules. Consequently, the relativistic formulation of nuclear spin-rotation (NSR) tensor for linear molecules is very much the same as that for nonlinear molecules. So is the relativistic mapping between experimental NSR and NMR.

Noncollinear and Spin-Flip TDDFT in Multicollinear Approach.

Time-dependent density functional theory (TDDFT) is one of the most important tools for investigating the excited states of electrons. The TDDFT calculation for spin-conserving excitation, where collinear functionals are sufficient, has obtained great success and has become routine. However, TDDFT for noncollinear and spin-flip excitations, where noncollinear functionals are needed, is less widespread and still a challenge nowadays. This challenge lies in the severe numerical instabilities that root in the second-order derivatives of commonly used noncollinear functionals. To be free from this problem radically, noncollinear functionals with numerical stable derivatives are desired, and our recently developed approach, called the multicollinear approach, provides an option. In this work, the multicollinear approach is implemented in noncollinear and spin-flip TDDFT, and prototypical tests are given.