The recent theoretical and experimental activities in positronium (Ps) scattering by atoms and molecules are reviewed with special emphasis at low energies. We critically compare the results of different groups $-$ theoretical and experimental. The theoretical approaches considered include the $R$-matrix and close-coupling methods applied to Ps-H, Ps-He, and Ps-Li scattering, and a coupled-channel approach with a nonlocal model-potential for Ps scattering by H, He, H$_2$, Ne, Ar, Li, Na, K, Rb, Cs, and Ps and for pickoff quenching in Ps-He scattering. Results for scattering lengths, partial, total and differential cross sections as well as resonance and binding energies in different systems are discussed.
We assess the performance of molecular densityfunctional theory (MDFT) to predict hydration freeenergies of the small drug-like molecules benchmark,FreeSolv. MDFT in the hyper-netted chain approx-imation (HNC) coupled with a pressure correctionpredicts experimental hydration free energies of theFreeSolv database within 1 kcal/mol with an averagecomputation time of two cpu.min per molecule. Thisis the same accuracy as for simulation based free en-ergy calculations that typically require hundreds ofcpu.h or tens of gpu.h per molecule.
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…
Calculated state-of-the art results for solvation and ionization energies of thousands of organic molecules relevant to battery design
Ecole Polytechnique Fédérale de Lausanne（洛桑联邦理工学院）；University of Vienna（维也纳大学）；Uppsala University（乌普萨拉大学）；Vector Institute for Artificial Intelligence（人工智能向量研究所）；University of Toronto（多伦多大学）；Technische Universität Berlin（柏林工业大学）
Accurate predictions of interatomic energies and forces are essential for high quality molecular dynamic simulations (MD). Machine learning algorithms can be used to overcome limitations of classical MD by predicting ab initio quality energies and forces. SE(3)-equivariant neural network allow reasoning over spatial relationships and exploiting the rotational and translational symmetries. One such algorithm is the SE(3)-Transformer, which we adapt for the ANI-1x dataset. Our early experimental results indicate through ablation studies that deeper networks - with additional SE(3)-Transformer la…
Heavy-atom alkaline earth monofluoride molecules are considered as prospective systems to study spatial parity or spatial parity and time-reversal symmetry violating effects such as the nuclear anapole moment or the electron electric dipole moment. Comprehensive and highly accurate theoretical study of the electronic structure properties and transition energies in such systems can simplify the preparation and interpretation of the experiments. However, almost no attempts to calculate quantum electrodynamics (QED) effects contribution into characteristics of neutral heavy-atom molecules have be…
Exchange and correlation energies of ground states of atoms and molecules in strong magnetic fields
采用Hartree-Fock网格方法和基于广义高斯基组的组态相互作用方法，研究了在B=0- 100 a. u的磁场中，氦原子、锂原子和氢分子的交换能和关联能的行为.一般来说，交换能对原子或分子的结合性质的重要性随着场强的增加而强烈地增加。这是由于自旋翻转跃迁，特别是由于紧密结合的类氢态的贡献，这些类氢态参与了不同对称性的相应基态。与交换能相反，相关能随着场强的增加而变得不那么相关。这适用于构成基态的各个构型和全局基态的交叉。
Effect of dipole polarizability on positron binding by strongly polar molecules
正电子与极性分子结合的模型被认为是由分子外的偶极势与一个强排斥的核心，一个给定的半径相结合。使用现有的结合能的实验数据导致非物理小核心半径的所有分子的研究。这表明，在简单模型中被忽略的电子-正电子相关性在确定结合能方面起着重要作用。我们占这些包括通过微扰理论和非微扰极化电位。微扰模型对一系列极性有机分子和氰化氢的结合能进行了可靠的预测。该模型还与从实验数据推断的结合能对极化率的线性依赖性一致[Danielson等人2009 J. Phys. B：At.摩尔光学物理学42 235203]。然而，对于大多数分子来说，有效的核心半径仍然是非物理性的小。非微扰处理分子极化导致物理上有意义的核心半径的所有分子的研究，并使更准确的预测结合能几乎所有的分子考虑。
A finite-element Delta-Sternheimer approach for computing accurate all-electron RPA correlation energies of polyatomic molecules
Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；School of Physical Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）；SKLMS, ICMSEC, NCMIS, Academy of Mathematics and Systems Science, Chinese Academy of Sciences（中国科学院数学与系统科学研究院）；School of Mathematical Sciences, University of Chinese Academy of Sciences（中国科学院大学数学科学学院）
The distribution of molecules between the gas and solid phase during star and planet formation, determines the trajectory of gas and grain surface chemistry, as well as the delivery of elements to nascent planets. This distribution is primarily set by the binding energies of different molecules to water ice surfaces. We computationally estimated the binding energies of ten astrochemically relevant P-bearing species on water surface, we also validate our method for 20 species with known binding energies. We used DFT calculations (M06-2X/aug-cc-pVDZ) to calculate the energetics of molecules and …
Atoms in molecules from alchemical perturbation density functional theory
在热力学积分的基础上，利用炼金术微扰密度泛函理论（APDFT）的无轨道框架，引入了分子中的原子（AIM）。在APDFT中，分子中的原子能量和电子密度是任意的，因为只要满足边界条件，就可以选择任意的参考系和积分路径。我们选择均匀的电子气作为最通用的参考，并线性放大所有的核电荷，位于任何查询分子的原子坐标。在计算单粒子电子密度时进行的近似中，这种选择提供了AIM能量和电子密度的准确且明确的定义。我们举例说明了中性等电子双原子的方法（CO，N $_2$，BF），具有碳的不同电子杂化状态的各种小分子（CH $_4$，C $_2$ H $_6$，C $_2$ H $_4$，C $_2$ H $_2$，HCN），以及所有可能的将苯连接到环硼氮烷的BN掺杂突变体（C $_{2n}$ B $_{3-n}$ N $_{3-n}$ H $_6$，$0 \le n \le 3$）。分析得到的数值结果表明，APDFT为基础的AIM使有意义的和新的解释的分子能量和电子密度。
Constructing accurate, high dimensional molecular potential energy surfaces (PESs) for polyatomic molecules is challenging. Reproducing Kernel Hilbert space (RKHS) interpolation is an efficient way to construct such PESs. However, the scheme is most effective when the input energies are available on a regular grid. Thus the number of reference energies required can become very large even for penta-atomic systems making such an approach computationally prohibitive when using high-level electronic structure calculations. Here an efficient and robust scheme is presented to overcome these limitati…
The cluster-in-molecule (CIM) local correlation approach with an accurate distant pair correlation energy correction is presented. For large systems, the inclusion of distant pair correlation energies is essential for the accurate predictions of absolute correlation energies and relative energies. Here we propose a simple and efficient scheme for evaluating the distant pair correlation energy correction. The corrections can be readily extracted from electron correlation calculations of clusters with almost no additional effort. Benchmark calculations show that the improved CIM approach can rec…
There has been great progress in developing methods for machine-learned potential energy surfaces. There have also been important assessments of these methods by comparing so-called learning curves on datasets of electronic energies and forces, notably the MD17 database. The dataset for each molecule in this database generally consists of tens of thousands of energies and forces obtained from DFT direct dynamics at 500 K. We contrast the datasets from this database for three "small" molecules, ethanol, malonaldehyde, and glycine, with datasets we have generated with specific targets for the PE…
Highly accurate theoretical predictions of transition energies in the radium monofluoride molecule, $^{226}$RaF and radium cation, $^{226}$Ra$^+$, are reported. The considered transition $X~^2Σ_{1/2} \to A~^2Π_{1/2}$ in RaF is one of the main features of this molecule and can be used to laser cool RaF for subsequent measurement of the electron electric dipole moment. For molecular and atomic predictions we go beyond the Dirac-Coulomb Hamiltonian and treat high-order electron correlation effects within the coupled cluster theory with the inclusion of quadruple and ever higher amplitudes. Effect…
Electrochemical setup - a unique chance to simultaneously control orbital energies and vibrational properties of single-molecule junctions with unprecedented efficiency
(Semi)-local density functional approximations (DFAs) suffer from self-interaction error (SIE). When the first ionization energy (IE) is computed as the negative of the highest-occupied orbital (HO) eigenvalue, DFAs notoriously underestimate them compared to quasi-particle calculations. The inaccuracy for the HO is attributed to SIE inherent in DFAs. We assessed the IE based on Perdew-Zunger self-interaction corrections on 14 small to moderate-sized organic molecules relevant in organic electronics and polymer donor materials. Though self-interaction corrected DFAs were found to significantly …
We revisit here the lowest vertical excitations of cyanine dyes using quantum Monte Carlo and leverage on recent developments to systematically improve on previous results. In particular, we employ a protocol for the construction of compact and accurate multi-determinant Jastrow-Slater wave functions for multiple states, which we have recently validated on the excited-state properties of several small prototypical molecules. Here, we obtain quantum Monte Carlo excitation energies in excellent agreement with high-level coupled cluster for all the cyanines where the coupled cluster method is app…
A quantum chemical study from a molecular perspective: ionization and electron attachment energies for species often used to fabricate single-molecule junctions
准确测定嵌入分子结中的分子的最低电子附着（$EA$）和电离（$IP$）能量对于正确估计\emph{e.g.}、电流（$I$）或偏置（$V$）的幅度（其中$I-V$曲线表现出显著的非欧姆行为）是重要的。用于制备n型导电单分子结的几种典型分子的最低电子附着能和电离能的基准计算（4，4 '-联吡啶、1，4-二氰基苯和4，4'-二氰基-1，1 '-联苯）和p型导电（苯二硫醇，联苯二硫醇，己烷单硫醇，基于EOM-CCSD（equation-of-motion coupled-cluster singles and doubles）的量子化学方法，研究了正己二硫醇与正己二硫醇之间的相互作用。它们表明与目前分子运输方法中获得的结果存在显着差异。本研究强调，除了一个可靠的量子化学方法，基组比无处不在的双zeta设置用于运输计算更好的是必要的。后者对于正确地确定$EA$是特别关键的问题，这在不包括足够的扩散基函数的情况下是不可能的。主导分子轨道（MO）的空间分布是另一个重要的问题，本研究引起了人们的注意，因为它敏感地影响由于在电极中形成的图像电荷的MO-能量移动$Φ$。目前的结果不能证实电极之间中点的点状MO的常见假设，其实质上影响实际的$Φ$值。
Inspired by Grimme's simplified Tamm-Dancoff density functional theory approach [S. Grimme, J. Chem. Phys. \textbf{138}, 244104 (2013)], we describe a simplified approach to excited state calculations within the GW approximation to the self-energy and the Bethe-Salpeter equation (BSE), which we call sGW/sBSE. The primary simplification to the electron repulsion integrals yields the same structure as with tensor hypercontraction, such that our method has a storage requirement that grows quadratically with system size and computational timing that grows cubically with system size. The performanc…
Numerical local "hybrid" functional treatment of selected diatomic molecules: comparison of energies and multipole moments to conventional hybrid functionals
V. V. Karasiev在[J. Chem. Phys. { \bf 118}，8567（2003）]中提出的新的局部“混合”泛函以非局部混合泛函为基准。它们的性能测试的总和高占据轨道能量，以及选定的双原子分子的电矩。新的泛函，随着Hartree-Fock和非混合泛函，有限差分计算，这是独立的基础。计算了6- 311 G、6- 311 G ++G（3df，3 pd）和AUG-cc-pVnZ（n= 3，4，6）基组与Hartree-Fock和常规密度泛函方法结合时的总能量和电矩的基组误差。有限差分局部“杂交”和基组非局部杂交泛函的结果之间的比较表明，局部和非局部杂交泛函的总能量同意在基组误差。与基组误差相比，多极矩的离散性在幅度上较大，但仍然相当小（小于6- 311 G基组产生的误差）。因此，我们建议使用新的本地“混合”泛函时，精度预计是足够的，因为他们需要一个解决方案的只是微分科恩-沙姆方程，而不是积分微分的情况下的混合泛函。
