Variational Formulation of the Generalized Many-Body Expansion with Self-Consistent Charge Embedding: Simple and Correct Analytic Energy Gradient for Fragment-Based<i>ab Initio</i>Molecular Dynamics

Liu, Jie; Rana, Bhaskar; Liu, Kuan-Yu; Herbert, John M.

doi:10.1021/acs.jpclett.9b01214

Cited by 22 publications

(21 citation statements)

References 99 publications

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“…25 One way to go beyond a simple charge embedding model is to use the Embedded Many-Body Expansion of Manby and co-workers which uses atom-centered gaussians to represent electrostatic interactions of the environment and a simple empirical model for Pauli repulsion. 26 A slightly more sophisticated embedding method is the Variational Many-Body Expansion (VMBE), 27 which builds upon the 1-body X-Pol wavefunction, [28][29][30][31][32][33] introduced by Jiali Gao and co-workers. In the X-Pol wavefunction, the supersystem wavefunction is written as a Hartree-product of the monomer wavefunctions.…”

Section: Introductionmentioning

confidence: 99%

Making many-body interactions nearly pairwise additive: The polarized many-body expansion approach

Veccham

Head‐Gordon

2019

The Journal of Chemical Physics

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The Many-Body Expansion (MBE) is a useful tool to simulate condensed phase chemical systems, often avoiding the steep computational cost of usual electronic structure methods. However, it often requires higher than 2-body terms to achieve quantitative accuracy. In this work, we propose the Polarized MBE (PolBE) method where each MBE energy contribution is treated as an embedding problem. In each energy term, a smaller fragment is embedded into a larger, polarized environment and only a small region is treated at the high-level of theory using embedded mean-field theory. The role of polarized environment was found to be crucial in providing quantitative accuracy at the 2-body level. PolBE accurately predicts non-covalent interaction energies for a number of systems, including CO 2 , water, and hydrated ion clusters, with a variety of interaction mechanisms, from weak dispersion to strong electrostatics considered in this work. We further demonstrate that the PolBE interaction energy is predominantly pairwise unlike the usual vacuum MBE which requires higher-order terms to achieve similar accuracy. We numerically show that PolBE often performs better than other widely used embedded MBE methods such as the electrostatically embedded MBE.Owing to the lack of expensive diagonalization of Fock matrices and its embarrassingly parallel nature, PolBE is a promising way to access condensed phase systems with hybrid density functionals that are difficult to treat with currently available methods.

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Section: Introductionmentioning

confidence: 99%

Making many-body interactions nearly pairwise additive: The polarized many-body expansion approach

Veccham

Head‐Gordon

2019

The Journal of Chemical Physics

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“…Our previous calculations showed that the neglect of these terms is a reasonable approximation if the PBC‐GEBF approach is applied for crystal structure optimizations and vibrational frequency calculations 63 . However, previous work have shown that terms from charge‐response contributions to the gradients may be important in extending fragment‐based approaches to MD simulations 68 …”

Section: Methodsmentioning

confidence: 99%

“…63 However, previous work have shown that terms from charge-response contributions to the gradients may be important in extending fragment-based approaches to MD simulations. 68 Furthermore, the second-order energy or even higher derivatives of a periodic system within the PBC-GEBF approach (or the corresponding properties) is similar to that described previously by our group for large molecules using the following formula 60…”

Section: The Pbc-gebf Approachmentioning

confidence: 97%

Structures and properties of ionic crystals and condensed phase ionic liquids predicted with the generalized energy‐based fragmentation method

Wang

et al. 2022

J Comput Chem

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The generalized energy-based fragmentation (GEBF) approach is extended to facilitate ab initio investigations of structures, lattice energies, vibrational spectra and 1 H NMR chemical shifts of ionic crystals and condensed-phase ionic liquids (ILs) with the periodic boundary conditions (PBC). For selected periodic systems, our results demonstrate that the so-called PBC-GEBF approach can provide satisfactory descriptions on ground-state energies, structures, and vibrational spectra of ionic crystals and IL crystals. The PBC-GEBF approach is then applied to three realistic condensed phase systems. For three ionic crystals (LiCl, NaCl, and KCl), we apply the PBC-GEBF approach with MP2 theory as well as some popular DFT methods to investigate their crystal structures and lattice energies. Our calculations indicate that the crystal structures obtained with PBC-GEBF-MP2/6-311 + G** are very close to the corresponding X-ray structures, while PBC-GEBF-ωB97X-D/6-311 + G** provides satisfactory prediction for crystal structures and lattice energies. For two polymorphs of [n-C 4 mim][Cl] crystals, we

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“…The converged charges are readily obtained from individual subsystem calculations as per Equation (12). Our treatment is similar to that of Liu et al in the context of GMBE [32] where self-consistent charges on the monomers in the many-body expansion are used. The inexpensive nature of MIM1 calculations lets us perform this iterative method without a significant increase in computational cost.…”

Section: Ee-mim Methodsmentioning

confidence: 99%

Electrostatically embedded molecules‐in‐molecules approach and its application to molecular clusters

2021

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We report the application of our fragment-based quantum chemistry model MIM (Molecules-In-Molecules) with electrostatic embedding. The method is termed "EE-MIM (Electrostatically Embedded Molecules-In-Molecules)" and accounts for the missing electrostatic interactions in the subsystems resulting from fragmentation. Point charges placed at the atomic positions are used to represent the interaction of each subsystem with the rest of the molecule with minimal increase in the computational cost. We have carefully calibrated this model on a range of different sizes of clusters containing up to 57 water molecules. The fragmentation methods have been applied with the goal of reproducing the unfragmented total energy at the MP2/6-311G(d,p) level. Comparative analysis has been carried out between MIM and EE-MIM to gauge the impact of electrostatic embedding. Performance of several different parameters such as the type of charge and levels of fragmentation are analyzed for the prediction of absolute energies. The use of background charges in subsystem calculations improves the performance of both one-and two-layer MIM while it is noticeably important in the case of one-layer MIM. Embedded charges for two-layer MIM are obtained from a full system calculation at the low-level. For onelayer MIM, in the absence of a full system calculation, two different types of embedded charges, namely, Geometry dependent (GD) and geometry independent (GI) charges, are used. A self-consistent procedure is employed to obtain GD charges. We have further tested our method on challenging charged systems with stronger intermolecular interactions, namely, protonated ammonia clusters (containing up to 30 ammonia molecules). The observations are similar to water clusters with improved performance using embedded charges. Overall, the performance of NPA charges as embedded charges is found to be the best.

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Variational Formulation of the Generalized Many-Body Expansion with Self-Consistent Charge Embedding: Simple and Correct Analytic Energy Gradient for Fragment-Basedab InitioMolecular Dynamics

Cited by 22 publications

References 99 publications

Making many-body interactions nearly pairwise additive: The polarized many-body expansion approach

Making many-body interactions nearly pairwise additive: The polarized many-body expansion approach

Structures and properties of ionic crystals and condensed phase ionic liquids predicted with the generalized energy‐based fragmentation method

Electrostatically embedded molecules‐in‐molecules approach and its application to molecular clusters

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