arXiv subjects

Wenjian Liu

Publications and source records attributed to Wenjian Liu.

At least 19 recordsLinked to original sources

arXiv2026

RoES: Rotational Equivariant Selective-frequency Fusion for Multimodal Images

Infrared-visible image fusion facilitates robust multimodal perception by integrating complementary textural nuances from visible sensors with thermal signatures from infrared systems. Due to the task's inherently ill-posed nature, existing methods heavily rely on structural priors but typically enforce rotation equivariance uniformly across all features. Such a holistic approach overlooks a critical distinction where low-frequency shared structures strictly adhere to equivariant constraints while high-frequency modality-specific details require greater flexibility to preserve unique information. To bridge this gap, we propose RoES, a Rotational Equivariant Selective-frequency fusion network. Instead of employing static decomposition, we introduce a trainable rotation-enhanced updater/predictor module to dynamically decouple low- and high-frequency components. The resulting representations are then processed through a dual-branch fusion module tailored for spectral consistency. Specifically, a rotation-equivariant Mamba is employed to capture long-range structural dependencies in the low-frequency domain, while a polar spectral attention-based Dual-Fourier block refines high-frequency details under explicit low-frequency guidance. Extensive experiments demonstrate that RoES consistently achieves state-of-the-art performance in both fusion quality and downstream object detection, establishing a robust solution for multimodal fusion by reconciling frequency-selective features with equivariant constraints. The source code is available at https://github.com/BryceLosky/RoES-Fusion.

cs.CV↗

arXiv2026

On the bottom-up construction of many-electron relativistic QED Hamiltonian

It was shown more than a decade ago [J. Chem. Phys. 139, 014108 (2013)] that a many-electron relativistic quantum electrodynamics (QED) Hamiltonian for high-precision electronic structure calculations can be constructed in a bottom-up fashion, by virtue of charge-conjugated contraction (CCC) of fermion operators when normal-ordering the starting unbounded relativistic Hamiltonian (second-quantized in terms of the electronic Dirac field) with respect to the filled negative-energy Dirac sea of electrons. It is shown here that the same relativistic QED Hamiltonian can also be obtained by equal average of the two relativistic Hamiltonians resulting from the normal-ordering of the starting unbounded relativistic Hamiltonians (second-quantized in terms of the electronic and positronic Dirac fields, respectively) with respect to the filled negative-energy Dirac seas of electrons and positrons, respectively, via the standard contraction of fermion operators. In essence, both procedures incorporate properly the fundamental charge-conjugation symmetry of relativistic quantum mechanics to ensure the symmetric treatment of the electronic and positronic degrees of freedom.

physics.chem-ph↗

arXiv2026

Putting PASPT2 on a Firmer Basis

The recently proposed partial-active-space (PAS) multi-state second-order perturbation theory (PASPT2) [Precis. Chem. 4, 997 (2026)] features connected amplitudes and a connected, closed intermediate Hamiltonian. Despite these hallmarks, PASPT2 (denoted as PASPT2H from now on) is not strictly size-extensive, as originally thought (and numerically confirmed), albeit strictly size-consistent. Nevertheless, PASPT2 is near-extensive for the states with major projections on the chosen PAS $\mathcal{M}_0$. This becomes more transparent upon introducing PASPT2X, a strictly size-extensive variant. Compared with the intruder-prone PASPT2X, the intruder-free PASPT2H merely neglects the second-order corrections that are important only for those states with major projections on the orthogonal complement $\mathcal{R}_X$ of $\mathcal{M}_0$ within the closed space $\mathcal{M}_X$ ($=\mathcal{M}_0\oplus\mathcal{R}_X$); however, such states are not supported by the chosen finite one-particle basis set. The weak violation of size-extensivity is therefore numerically insignificant for the target states supported by $\mathcal{M}_0$, reinforcing the theoretical basis of PASPT2H.

physics.chem-ph↗

arXiv2026

Fundus Image-based Glaucoma Screening via Retinal Knowledge-Oriented Dynamic Multi-Level Feature Integration

While deep learning has advanced automated glaucoma screening via color fundus photography, existing purely data-driven models often overfit to confounding imaging artifacts and struggle to capture unpredictable pathological cues located beyond predefined anatomical boundaries. To address these limitations, we propose a retinal knowledge-oriented framework that synergizes dynamic multi-scale feature learning with domain-specific anatomical priors. The proposed architecture adopts a tri-branch structure to jointly model the global retinal context, the structural characteristics of the optic cup and disc, and dynamically cropped pathological regions. Specifically, we devise a Dynamic Window Mechanism (DWM) that adaptively discovers diagnostically informative patches via image-level supervision. Furthermore, we introduce a Knowledge-Enhanced Convolutional Block Attention Module (KE-CBAM) that explicitly incorporates retinal priors from a pre-trained foundation model RETFound to guide spatial attention, preventing the network from assigning spurious weights to irrelevant background noise. Extensive evaluations on the large-scale AIROGS dataset demonstrate that our method achieves a state-of-the-art AUC of $98.5\%$ and an accuracy of $94.6\%$. More importantly, the integration of anatomical priors effectively mitigates the inherent class imbalance, significantly improving the detection of referable glaucoma cases. Additional validations on the SMDG-19 benchmark further confirm its superior cross-domain generalization, indicating that our contribution provides a robust, interpretable, and scalable solution for real-world clinical glaucoma diagnosis. Our code is available at https://github.com/magiczhuo/Glaucoma-Detection

cs.CV↗

arXiv2026

cQED-iCIPT2: A Near-Exact Method for Polaritonic Chemistry

Strong light-matter coupling in optical cavities provides a versatile platform for modulating chemical structure, reactivity, and spectroscopy, and hence motivates the development of ab initio cavity quantum electrodynamics (cQED) methods that can treat the electronic and photonic degrees of freedom on an equal footing. We present such a method, cQED-iCIPT2, by combining the near-exact iCIPT2 (iterative configuration interaction with selection and second-order perturbation theory) with the cQED Hamiltonian in two ways, cQED-PN-iCIPT2 and cQED-CS-iCIPT2. The former works directly in the photon-number representation, whereas the latter employs a coherent-state transformation that restores origin invariance of the cQED Hamiltonian and avoids artificially strong coupling in charged systems. To efficiently handle the tensor-product structure of the electron-photon wavefunction, we introduce a graded configuration space organized by photon numbers and decompose the key computational steps (selection, diagonalization, and perturbation correction) into intra- and inter-subspace steps, so as to maximize the reuse of the existing infrastructure in the MetaWave platform (J. Phys. Chem. A 2025, 129, 5170). The selection step enables automatic determination of the optimal number of photons without a priori truncation. The efficacy of the methods is showcased dissociation of N2, torsion of ethylene, proton transfer reactions in malonaldehyde and aminopropenal, and low-lying excited states of polyacenes. The results provide numerically accurate reference data and meanwhile reveal how the cavity can fine-tune reaction barriers, alter potential energy surfaces, and induce state crossings. As such, this work establishes a robust near-exact framework for polaritonic chemistry in the presence of both strong electron correlation and strong light-matter coupling.

physics.chem-ph↗

arXiv2026

Analytic first-order non-adiabatic coupling matrix elements of spin-adapted open-shell time-dependent density functional theory

While spin-adapted time-dependent density functional theory (TDDFT) approaches significantly improve the excitation energies and gradients of open-shell molecules, the effect of spin-adaptation on non-adiabatic coupling matrix elements (NACMEs) remains unknown for spin-conserving excitations. In this article, we report the derivation, implementation and benchmark studies of the ground state-excited state and excited state-excited state NACMEs of our spin-adapted TDDFT method, X-TDDFT; to our best knowledge, this represents the first implementation of the analytic NACMEs of a spin-adapted TDDFT method. Similar to the X-TDDFT analytic gradients, X-TDDFT NACMEs can be easily implemented on top of an existing U-TDDFT NACME implementation taking into account the restricted open-shell Kohn-Sham (ROKS) reference and the implicit involvement of doubly excited determinants, with acceptable computational overhead. Benchmark calculations reveal that X-TDDFT reduces the error of U-TDDFT NACMEs by 1/3-2/3 (referenced against high-level multireference NACMEs), which leads to large corrections of internal conversion rates (up to two orders of magnitude). In particular, for copper(II) porphyrin, X-TDDFT leads to qualitative revisions of the relative importance of the excited state relaxation pathways, as well as the substituent effects of the internal conversion (IC) rates, suggesting that the error of U-TDDFT NACMEs is not only large but also unsystematic. It is therefore expected that X-TDDFT NACMEs will prove useful in the photophysics/photochemistry studies of open-shell systems such as radicals and transition metal complexes.

physics.chem-ph↗

arXiv2026

PASPT2: a size-extensive and size-consistent partial-active-space multi-state multi-reference second-order perturbation theory for strongly correlated electrons

A partial-active-space (PAS) multi-state (MS) multi-reference second-order perturbation theory (MRPT2) for the electronic structure of strongly correlated systems of electrons, dubbed PASPT2, is formulated by linearizing the intermediate normalization-based general-model-space state-universal coupled-cluster theory with singles and doubles [IN-GMS-SU-CCSD; J. Chem. Phys. 119, 5320 (2003)]. At variance with the existence of disconnected terms in the IN-GMS-SU-CCSD amplitude equations, the disconnected terms in the PASPT2 amplitude equations can be avoided completely by choosing a special reference-specific zeroth-order Hamiltonian. The corresponding effective/intermediate Hamiltonian can also be made connected and closed, so as to render the energies obtained by diagonalization fully connected. As such, PASPT2 is strictly size-extensive, in sharp contrast with the parent IN-GMS-SU-CCSD. It is also size-consistent when the PAS of a supermolecule is chosen to be the direct product of those of the physically separated, non-interacting fragments. Prototypical systems are taken as showcases to reveal the efficacy of PASPT2.

physics.chem-ph↗

arXiv2026

Fast and accurate committor estimation for kinetics simulations

Computing long-timescale kinetics of biomolecular processes remains a major challenge for atomistic simulations. A way out is to exploit local kinetic information to construct the global stationary flux across the reaction space. The committor serves as the optimal reaction coordinate for this purpose; however, its calculation is itself highly demanding. Here, we introduce a fast and accurate algorithm for committor estimation by leveraging highly parallelizable short trajectory simulations and analogue prediction. The resulting committor is represented via a neural network ansatz and subsequently coupled with the Milestoning method to predict the mean first passage time at very low computational cost. We demonstrate the robustness and efficiency of this committor-guided Milestoning (CoM) method through examples of increasing complexity.

physics.chem-ph↗

arXiv2026

Unified MPI Parallelization of Wave Function Methods: iCIPT2 as a Showcase

The integration of quantum chemical methods with high-performance computing is indispensable for handling large systems with modest accuracy or even small systems but with high accuracy. Continuing with the unified implementation of non-relativistic and relativistic wave functions methods within the MetaWave platform (J. Phys. Chem. A. 2025, 129, 5170), we present here a unified MPI parallelization of the methods by abstracting ever computational step of a method as a dynamically-scheduled loop via ghost process, followed by a global reduction of local results from each node. The algorithmic abstraction enables the use of a single MPI template in various steps of different methods. Taking iCIPT2 [J. Chem. Theory Comput. 2021, 17, 949] as a showcase, the parallel efficiencies achieve 94% and 89% on 16 nodes (1024 cores) for the perturbation and whole calculations, respectively. Further combined with an improved algorithm for the matrix-vector product in the matrix diagonalization and an orbital-configuration-based semi-stochastic estimator for the perturbation correction, this renders large active space calculations possible, so as to obtain benchmarks for the automerization of cyclobutadiene, ground state energy of benzene and potential energy profile of ozone. It is also shown that the error of iCIPT2 follows a power law with respect to the number of configuration state functions.

physics.chem-ph↗

arXiv2025

O1NumHess: a fast and accurate seminumerical Hessian algorithm using only O(1) gradients

In this work, we describe a new algorithm, O1NumHess, to calculate the Hessian of a molecular system by finite differentiation of gradients calculated at displaced geometries. Different from the conventional seminumerical Hessian algorithm, which requires gradients at $O(N_{\mathrm{atom}})$ displaced geometries (where $N_{\mathrm{atom}}$ is the number of atoms), the present approach only requires $O(1)$ gradients. Key to the reduction of the number of gradients is the exploitation of the off-diagonal low-rank (ODLR) property of Hessians, namely the blocks of the Hessian that correspond to two distant groups of atoms have low rank. This property reduces the number of independent entries of the Hessian from $O(N_{\mathrm{atom}}^2)$ to $O(N_{\mathrm{atom}})$, such that $O(1)$ gradients already contain enough information to uniquely determine the Hessian. Numerical results on model systems (long alkanes and polyenes), transition metal reactions (WCCR10) and non-covalent complexes (S30L-CI) using the BDF program show that O1NumHess gives frequency, zero-point energy, enthalpy and Gibbs free energy errors that are only about two times those of conventional double-sided seminumerical Hessians. Moreover, O1NumHess is always faster than the conventional numerical Hessian algorithm, frequently even faster than the analytic Hessian, and requires only about 100 gradients for sufficiently large systems. An open-source implementation of this method, which can also be applied to problems irrelevant to computational chemistry, is available on GitHub.

physics.chem-ph↗

arXiv2025

MetaWave: A Platform for Unified Implementation of Nonrelativistic and Relativistic Wavefunctions

\texttt{MetaWave} is a C++ template-based architecture designed for unified implementation of nonrelativistic and relativistic wavefunction-based quantum chemical methods. It is highly modular, extendable, and efficient. This is achieved by decoupling the three distinct aspects of quantum chemical methods (i.e., nature of Hamiltonian, structure of wavefunction, and strategy of parallelization ), thereby allowing for separate treatment of them through their internal type-trait and tagging systems furnished by C++ metaprogramming. Once the second-quantized Hamiltonians, whether nonrelativistic (spin-free) or relativistic (spin-dependent), are decomposed into topologically equivalent diagrams for a unified evaluation of the basic coupling coefficients between (randomly selected) spin-free or spin-dependent configuration state functions or Slater determinants incorporating full molecular symmetry (including single or double point group and spin or time reversal symmetry), the many-electron wavefunctions, whether built up with scalar or spinor orbitals, can be assembled with the same templates. As for parallelization, \texttt{MetaWave} supports both OpenMP and MPI, with the majority of the latter being translated automatically from its OpenMP counterparts.The whole structure of \texttt{MetaWave} is reviewed here, with some showcases for illustrating its performance.

physics.chem-ph↗

arXiv2025

Magnetic topological Weyl fermions in half-metallic In$_2$CoSe$_4$

Magnetic Weyl semimetals (WSM) have recently attracted much attention due to their potential in realizing strong anomalous Hall effects. Yet, how to design such systems remains unclear. Based on first-principles calculations, we show here that the ferromagnetic half-metallic compound In$_2$CoSe$_4$ has several pairs of Weyl points and is hence a good candidate for magnetic WSM. These Weyl points would approach the Fermi level gradually as the Hubbard $U$ increases, and finally disappear after a critical value $U_c$. The range of the Hubbard $U$ that can realize the magnetic WSM state can be expanded by pressure, manifesting the practical utility of the present prediction. Moreover, by generating two surface terminations at Co or In atom after cleaving the compound at the Co-Se bonds, the nontrivial Fermi arcs connecting one pair of Weyl points with opposite chirality are discovered in surface states. Furthermore, it is possible to observe the nontrivial surface state experimentally, e.g., angle-resolved photoemission spectroscopy (ARPES) measurements. As such, the present findings imply strongly a new magnetic WSM which may host a large anomalous Hall conductivity.

cond-mat.mtrl-sci↗

arXiv2024

SDSPT2s: SDSPT2 with Selection

As an approximation to SDSCI [static-dynamic-static (SDS) configuration interaction (CI), a minimal MRCI; Theor. Chem. Acc. 133, 1481 (2014)], SDSPT2 [Mol. Phys. 115, 2696 (2017)] is a CI-like multireference (MR) second-order perturbation theory (PT2) that treats single and multiple roots on an equal footing. This feature permits the use of configuration selection over a large complete active space (CAS) $P$ to end up with a much reduced reference space $\tilde{P}$, which is connected only with a portion ($\tilde{Q}_1$) of the full first-order interacting space $Q$ connected to $P$. The effective interacting $\tilde{Q}$ space can further be truncated by an integral-based cutoff threshold. With marginal loss of accuracy, the selection-truncation procedure, along with an efficient evaluation and storage of internal contraction coefficients, renders SDSPT2s (SDSPT2 with selection) applicable to systems that cannot be handled by the parent CAS-based SDSPT2, as demonstrated by several challenging showcases.

physics.chem-ph↗

arXiv2024

QUEST\#4X: an extension of QUEST\#4 for benchmarking multireference wavefunction methods

Given a number of datasets for evaluating the performance of single reference methods for the low-lying excited states of closed-shell molecules, a comprehensive dataset for assessing the performance of multireference methods for the low-lying excited states of open-shell systems is still desired. For this reason, we propose an extension (QUEST\#4X) of the radial subset of QUEST\#4 [J. Chem. Theory Comput. 2020, 16, 3720] to cover 110 doublet and 39 quartet excited states. Near-exact results obtained by iCIPT2 (iterative configuration interaction with selection and second-order perturbation correction) are taken as benchmark to calibrate SDSCI (static-dynamic-static configuration interaction) and SDSPT2 (static-dynamic-static second-order perturbation theory), which are minimal MRCI and CI-like perturbation theory, respectively. It is found that SDSCI is very close in accuracy to ic-MRCISD (internally contracted multireference configuration interaction with singles and doubles), although its computational cost is just that of one iteration of the latter. Unlike most variants of MRPT2, SDSPT2 treats single and multiple states in the same way, and performs similarly as MS-NEVPT2 (multi-state n-electron valence second-order perturbation theory). These findings put SDSCI and SDSPT2 on a firm basis.

physics.chem-ph↗

arXiv2024

Accelerating Fock build via hybrid analytical-numerical integration

A very robust and efficient hybrid analytic-numerical Fock build, aMECP+aCOSx, has been developed for accelerating HF/DFT calculations. The essential idea is to extract those portions of the Fock matrix that can readily be evaluated analytically, so as to minimize numerical noises arising from the semi-numerical and numerical integrations. As a result, the combination of aMECP with a medium grid and aCOSx with a coarse grid is already sufficient to achieve an accuracy of less than 1μEh/atom in total energies. The acceleration of aMECP+aCOSx over the analytic Fock build is already seen in calculations of small molecular systems and is more enhanced in calculations of large molecules with extended basis sets.

physics.chem-ph↗

arXiv2024

Milestoning network refinement by incorporating experimental thermodynamic and kinetic data

Milestoning is an accurate and efficient method for rare event kinetics calculations by constructing a continuous-time kinetic network connecting the reactant and product states. However, even with adequate sampling, its accuracy can also be limited by the force fields, which makes it challenging to achieve quantitative agreement with experimental data. To address this issue, we present a refinement approach by minimizing the Kullback-Leibler divergence rate between two Milestoning networks while incorporating experimental thermodynamic (equilibrium constants) and kinetic (rate constants) data as constraints. This approach ensures that the refined kinetic network is minimally perturbed with respect to the original one, while simultaneously satisfying the experimental constraints. The refinement approach is demonstrated using the binding and unbinding dynamics of a series of six small molecule ligands for the model host system, $β$-cyclodextrin.

physics.chem-ph↗

arXiv2024

Unified Implementation of Relativistic Wave Function Methods: 4C-iCIPT2 as a Showcase

In parallel to the unified construction of relativistic Hamiltonians based solely on physical arguments [J. Chem. Phys. 160, 084111 (2024)], a unified implementation of relativistic wave function methods is achieved here via programming techniques (e.g., template metaprogramming and polymorphism in C++). That is, once the code for constructing the Hamiltonian matrix is made ready, all the rest can be generated automatically from existing templates used for the nonrelativistic counterparts. This is facilitated by breaking a second-quantized relativistic Hamiltonian down to diagrams that are topologically the same as those required for computing the basic coupling coefficients between spin-free configuration state functions (CSF). Moreover, both time reversal and binary double point group symmetries can readily be incorporated into molecular integrals and Hamiltonian matrix elements. The latter can first be evaluated in the space of (randomly selected) spin-dependent determinants and then transformed to that of spin-dependent CSFs, thanks to simple relations in between. As a showcase, we consider here the no-pair four-component relativistic iterative configuration interaction with selection and perturbation correction (4C-iCIPT2), which is a natural extension of the spin-free iCIPT2 [J. Chem. Theory Comput. 17, 949 (2021)], and can provide near-exact numerical results within the manifold of positive energy states (PES), as demonstrated by numerical examples.

physics.chem-ph↗

arXiv2024

Response to "Response to 'Comment on Theoretical examination of QED Hamiltonian in relativistic molecular orbital theory'" [J. Chem. Phys. 160, 187102 (2024)]

The Response [J. Chem. Phys. 160, 187102 (2024)] of Inoue and coworkers to my Comment [J. Chem. Phys. 160, 187101 (2024)] on their original paper [J. Chem. Phys. 159, 054105 (2023)] clarifies some points put forward in my Comment, but also raises some new issues that require further clarifications. It is believed that the present Response has settled down everything.

physics.chem-ph↗