A one-electron Schroedinger equation based on special one-electron potentials for atoms is shown to exist that produces orbitals for an arbitrary molecule that are sufficiently accurate to be used without modification to construct single- and multi-determinant wavefunctions. The exact Hamiltonian is used to calculate the energy variationally and to generate configuration interaction expansions. Earlier work on equilibrium geometries is extended to larger basis sets and molecular dissociation. For a test set of molecules representing different bonding environments, a single set of invariant atomic potentials gives wavefunctions with energies that deviate from configuration interaction energies based on SCF orbitals by less than 0.04 eV per bond or valence electron pair. On a single diagonalization of the Fock matrix, the corresponding errors are reduced 0.01 eV. Atomization energies are also in good agreement with CI values based on canonical SCF orbitals. Configuration interaction applications to single bond dissociations of water and glycine, and multiple bond dissociations of ethylene and oxygen produce dissociation energy curves in close agreement with CI calculations based on canonical SCF orbitals for the entire range of internuclear distances.
A two-orbital two-electron diatomic model resembling LiH is used to investigate the differences between the exact Löwdin-Shull and approximate Hartree-Fock-Bogoliubov and Baerends-Buijse density matrix functionals in the medium- to long-distance dissociation region. In case of homolytic dissociation (one electron on each atom), the approximate functionals fail to generate the correct energy due to a compromise between the Hartree-Fock component (which favors partial charge transfer) and the strong correlation component (which hampers charge transfer). The exact functional is able to generate t…
Evidence of Photocatalytic Dissociation of Water on TiO2 with Atomic Resolution
TiO 2表面的光催化分解水反应是氢能技术中具有重要意义的基础问题之一，并得到了广泛的研究。然而，存在的第一个反应步骤，直接光解水，已被忽视。在这里，我们提供了明确的实验证据表明，吸附在金红石型TiO 2（110）-1 \times 1表面的水分子可以解离紫外线照射下，使用低温扫描隧道显微镜。结果表明，在光催化作用下，Ti（Ti_（5c））五配位上的一个水分子发生解离，在Ti_（5c）上生成一个羟基，在桥氧排上生成另一个羟基。我们的研究结果揭示了光催化水裂解反应链中缺失的一环，这大大有助于详细了解潜在的机制。
Current Non-Orthogonal Configuration Interaction (NOCI) methods often use a set of Self-Consistent Field (SCF) states selected based on chemical intuition. However, it may be challenging to track these SCF states across a dissociation profile and the NOCI states recovered may be spin contaminated. In this paper, we propose a method of applying spin rotation on symmetry broken UHF (sb-UHF) states to generate a basis for NOCI. The dissociation of ethene was examined by localising spin rotation on each resulting carbene fragment. We show that this gives a size-consistent description of its dissoc…
Time-dependent N-electron valence perturbation theory with matrix product state reference wavefunctions for large active spaces and basis sets: Applications to the chromium dimer and all-trans polyenes
在早期的工作[J. Chem. Phys. 144，064102（2016）]中，我们引入了二阶N电子价态微扰理论（t-NEVPT 2）的时间依赖性公式，其（i）具有比通常的内部收缩微扰公式更低的计算标度，并且（ii）产生完全未收缩的NEVPT 2能量。在这里，我们提出了一个组合的t-NEVPT 2与矩阵产品状态（MPS）的参考波函数（t-MPS-NEVPT 2），允许计算未收缩的动态相关能量为大的活性空间和基组，使用时间相关的密度矩阵重整化群（TD-DMRG）算法。此外，我们报告了一个低尺度的MPS为基础的实施强收缩NEVPT 2（sc-MPS-NEVPT 2），避免了计算的四粒子约简密度矩阵。我们使用这些新的方法来计算的铬二聚体的解离能和研究的低-躺在激发态的全反式多烯（C $_4$ H $_6$ C $_{24}$ H $_{26}$），将动态相关的参考波函数与多达24个活性电子和轨道。
For a given many-electron molecule, it is possible to define a corresponding one-electron Schrödinger equation, using potentials derived from simple atomic densities, whose solution predicts fairly accurate molecular orbitals for single- and multi-determinant wavefunctions for the molecule. The energy is not predicted and must be evaluated by calculating Coulomb and exchange interactions over the predicted orbitals. Transferable potentials for first-row atoms and transition metal oxides that can be used without modification in different molecules are reported. For improved accuracy, molecular …
A general procedure for the optimization of atomic density-fitting basis functions is designed with the balance between accuracy and numerical stability in mind. Given one-electron wavefunctions and energies, weights are assigned to the product densities, modeling their contribution to the exchange and second-order correlation energy, and a simple weighted error measure is minimized. Generally-contracted Gaussian auxiliary basis sets are optimized to match the wavefunction basis sets [D. N. Laikov, Theor. Chem. Acc. 138, 40 (2019)] for all 102 elements in a scalar-relativistic approximation [D…
Leveraging ab initio data at scale has enabled the development of machine learning models capable of extremely accurate and fast molecular property prediction. A central paradigm of many previous works focuses on generating predictions for only a fixed set of properties. Recent lines of research instead aim to explicitly learn the electronic structure via molecular wavefunctions from which other quantum chemical properties can directly be derived. While previous methods generate predictions as a function of only the atomic configuration, in this work we present an alternate approach that direc…
Different Rise Times of Atomic Br M$_{4,5}$ 3d$_{3/2,5/2}$ Core Level Absorptions during Br$_{2}$ C $^{1}Π_{u}$ $1_{u}$ State Dissociation via Extreme Ultraviolet Transient Absorption Spectroscopy
Ground state eigenvectors of the reduced Bardeen-Cooper-Schrieffer Hamiltonian are employed as a wavefunction ansatz to model strong electron correlation in quantum chemistry. This wavefunction is a product of weakly-interacting pairs of electrons. While other geminal wavefunctions may only be employed in a projected Schrödinger equation, the present approach may be solved variationally with polynomial cost. The resulting wavefunctions are used to compute expectation values of Coulomb Hamiltionans and we present results for atoms and dissociation curves which are in agreement with doubly-occup…
We report on a many-electron wavefunction theory study for the reaction energetics of hydrogen dissociation on the Si(100) surface. We demonstrate that quantum chemical wavefunction based methods using periodic boundary conditions can predict chemically accurate results for the activation barrier and the chemisorption energy in agreement with experimental findings. These highly accurate results for the reaction energetics enable a deeper understanding of the underlying physical mechanism and make it possible to benchmark widely used density functional theory methods.
Resolving electronic evolution during bond dissociation
University of Ottawa（渥太华大学）；National Research Council（国家研究委员会）；Joint Center for Extreme Photonics（极端光子学联合中心）；Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences（中国科学院精密测量科学与技术创新研究院武汉物理与数学研究所）；Department of Physics, University of Central Florida（中佛罗里达大学物理系）；CNR IFN - Istituto di Fotonica e Nanotecnologie（意大利国家研究委员会光子和纳米技术研究所）
A detailed computational analysis has been performed, considering copper atomic contacts that are exposed directly to water molecules, hydroxyl groups, and monatomic as well as molecular hydrogen and oxygen species. The optimized physical bonding structure, electrical conductance and inelastic tunneling spectra (IETS) have been determined theoretically for moderately large structures by performing appropriate ab-initio and semi-empirical calculations. By considering the aforementioned properties, it has been possible to determine that some of the molecular bridging structures may be regarded a…
Quantum simulations of the hydroxide anion and hydroxyl radical are reported, employing variational quantum algorithms for near-term quantum devices. The energy of each species is calculated along the dissociation curve, to obtain information about the stability of the molecular species being investigated. It is shown that simulations restricted to valence spaces incorrectly predict the hydroxyl radical to be more stable than the hydroxide anion. Inclusion of dynamical electron correlation from non-valence orbitals is demonstrated, through the integration of the variational quantum eigensolver…
We investigate the renormalized perturbative triples correction together with the externally corrected coupled-cluster singles and doubles (ecCCSD) method. We take the density matrix renormalization group (DMRG) and heatbath CI (HCI) as external sources for the ecCCSD equations. The accuracy is assessed for the potential energy surfaces of H2O, N2, and F2. We find that the triples correction significantly improves on ecCCSD and we do not see any instability of the renormalized triples with respect to dissociation. We explore how to balance the cost of computing the external source amplitudes w…
Structural geometries, formation enthalpies, and dissociation energies of all diatomic and triatomic molecules consisting of the four basic elements C, H, N, and/or O are calculated from the projector augmented wave (PAW) density functional theory (DFT) method with the PBE and optB88-vdW exchange-correlation functionals. The calculations are also extended to two larger molecules NO3 and HNO3, which consist of 4 and 5 atoms, respectively. In total, 82 molecules or isomers are considered in the calculations. The geometric parameters including 42 bond lengths and 15 bond angles of these molecules…
NucleoNet: A Nuclear-Aware Determinant Ansatz for Multi-Geometry Neural Variational Monte Carlo
School of Artificial Intelligence and Data Science, University of Science and Technology of China（中国科学技术大学人工智能与数据科学学院）；University of Science and Technology of China（中国科学技术大学）；Suzhou Institute for Advanced Research, University of Science and Technology of China（中国科学技术大学苏州高等研究院）；Singapore University of Technology and Design（新加坡科技设计大学）；AI for Science Institute（北京智源人工智能研究院）；School of Mathematical Sciences, University of Science and Technology of China（中国科学技术大学数学科学学院）；National Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics（应用物理与计算数学研究部计算物理国家实验室）；HEDPS, CAPT, College of Engineering, Peking University（北京大学工学院）
Aiming to combine density functional theory (DFT) and wavefunction theory, we study a mapping from the many-body interacting system to an effectively-interacting Kohn-Sham system instead of a non-interacting Kohn-Sham system. Because a ground state of effectively-interacting systems requires having a solution for the correlated many-body wavefunctions, this provides a natural framework to many-body wavefunction theories such as the configuration interaction and the coupled cluster method in the formal theoretical framework of DFT. Employing simple one-dimensional two-electron systems -- namely…
Referring to a recent experiment, we theoretically study the process of a two-channel decay of the diatomic silver anion (Ag$_2^-$), namely the spontaneous electron ejection giving Ag$_2$ + e$^-$ and the dissociation leading to Ag$^-$ + Ag. The ground state potential energy curves of the silver molecules of diatomic neutral and negative ion were calculated using proper pseudo-potentials and atomic basis sets. We also estimated the non-adiabatic electronic coupling between the ground state of Ag$_2^-$ and the ground state of Ag$_2$ + e$^-$, which in turn allowed us to estimate the minimal and m…
Given access to accurate solutions of the many-electron Schrödinger equation, nearly all chemistry could be derived from first principles. Exact wavefunctions of interesting chemical systems are out of reach because they are NP-hard to compute in general, but approximations can be found using polynomially-scaling algorithms. The key challenge for many of these algorithms is the choice of wavefunction approximation, or Ansatz, which must trade off between efficiency and accuracy. Neural networks have shown impressive power as accurate practical function approximators and promise as a compact wa…
Machine learning advances chemistry and materials science by enabling large-scale exploration of chemical space based on quantum chemical calculations. While these models supply fast and accurate predictions of atomistic chemical properties, they do not explicitly capture the electronic degrees of freedom of a molecule, which limits their applicability for reactive chemistry and chemical analysis. Here we present a deep learning framework for the prediction of the quantum mechanical wavefunction in a local basis of atomic orbitals from which all other ground-state properties can be derived. Th…
