scholarly journals Embedded, graph‐theoretically defined many‐body approximations for wavefunction‐in‐DFT and DFT‐in‐DFT : Applications to gas‐ and condensed‐phase ab initio molecular dynamics, and potential surfaces for quantum nuclear effects

2020 ◽  
Vol 120 (21) ◽  
Author(s):  
Timothy C. Ricard ◽  
Anup Kumar ◽  
Srinivasan S. Iyengar
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Condensed Phase ◽  
Ab Initio Molecular Dynamics ◽  
Many Body ◽  
Potential Surfaces ◽  
Embedded Graph ◽  
Nuclear Effects

scholarly journals Static and Dynamic Statistical Correlations in Water: Comparison of Classical Ab Initio Molecular Dynamics at Elevated Temperature With Path Integral Simulations at Ambient Temperature

2022 ◽  
Author(s):  
Chenghan Li ◽  
Francesco Paesani ◽  
Gregory A. Voth
Keyword(s):  
Molecular Dynamics ◽  
Elevated Temperature ◽  
Ambient Temperature ◽  
Ab Initio ◽  
Density Functional ◽  
Ab Initio Molecular Dynamics ◽  
Many Body ◽  
Statistical Correlations ◽  
Higher Temperature ◽  
The Many

It is a common practice in ab initio molecular dynamics (AIMD) simulations of water to use an elevated temperature to overcome the over-structuring and slow diffusion predicted by most current density functional theory (DFT) models. The simulation results obtained in this distinct thermodynamic state are then compared with experimental data at ambient temperature based on the rationale that a higher temperature effectively recovers nuclear quantum effects (NQEs) that are missing in the classical AIMD simulations. In this work, we systematically examine the foundation of this assumption for several DFT models as well as for the many-body MB-pol model. We find for the cases studied that a higher temperature does not correctly mimic NQEs at room temperature, which is especially manifest in significantly different three-molecule correlations as well as hydrogen bond dynamics. In many of these cases, the effects of NQEs are the opposite of the effects of carrying out the simulations at an elevated temperature.

scholarly journals Fragment-Based Ab Initio Molecular Dynamics Simulation for Combustion

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3120
Author(s):  
Liqun Cao ◽  
Jinzhe Zeng ◽  
Mingyuan Xu ◽  
Chih-Hao Chin ◽  
Tong Zhu ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Combustion Process ◽  
Computational Cost ◽  
Reaction Network ◽  
Methane Combustion ◽  
Dynamics Simulation ◽  
Ab Initio Molecular Dynamics ◽  
Many Body ◽  
Experimental Findings

We develop a fragment-based ab initio molecular dynamics (FB-AIMD) method for efficient dynamics simulation of the combustion process. In this method, the intermolecular interactions are treated by a fragment-based many-body expansion in which three- or higher body interactions are neglected, while two-body interactions are computed if the distance between the two fragments is smaller than a cutoff value. The accuracy of the method was verified by comparing FB-AIMD calculated energies and atomic forces of several different systems with those obtained by standard full system quantum calculations. The computational cost of the FB-AIMD method scales linearly with the size of the system, and the calculation is easily parallelizable. The method is applied to methane combustion as a benchmark. Detailed reaction network of methane reaction is analyzed, and important reaction species are tracked in real time. The current result of methane simulation is in excellent agreement with known experimental findings and with prior theoretical studies.

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