Connectivity-Based Parallel Replica Dynamics for Chemically Reactive Systems: From Femtoseconds to Microseconds

Joshi, Kaushik; Raman, Sumathy; Duin, Adri C. T. van

doi:10.1021/jz4019223

Cited by 57 publications

(55 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thirdly, the reliability of the predictions could be improved by shifting the simulation temperatures towards practical pyrolysis conditions. This could be feasible with recently introduced software and hardware acceleration methods, such as the accelerated ReaxFF reactive dynamics (aARRDyn) (Cheng et al 2014), reactive parallel replica dynamics (RPRD) (Joshi et al 2013) and the GPU-accelerated version of ReaxFF (Zheng et al 2013). Together, the suggested extensions would constitute a ReaxFF-MD framework for predicting the primary reaction pathways of cellulose pyrolysis, the associated kinetics and the main features of the product spectrum.…”

Section: Discussionmentioning

confidence: 99%

High-temperature decomposition of the cellulose molecule: a stochastic molecular dynamics study

Paajanen

Vaari

2017

Cellulose

View full text Add to dashboard Cite

The kinetics and products of cellulose pyrolysis can be studied using large-scale molecular dynamics simulations at high temperatures, where the reaction rates are high enough to make the simulation times practical. We carried out molecular dynamics simulations employing the ReaxFF reactive force field to study the initial step of the thermal decomposition process. We gathered statistics of simulated reactive events at temperatures ranging from 1400 to 2200 K, considering cellulose molecules with different molecular weights and initial conformations. Our simulations suggest that, in gas-phase conditions at these high temperatures, the decomposition occurs primarily through random cleavage of the b(1 ? 4)-glycosidic bonds, for which we obtained an activation energy of (171 ± 2) kJ mol -1 and a frequency factor of 1:07 AE 0:12 ð ÞÂ10 15 s -1 . We did not observe dependency of the kinetic parameters on the molecular weight or initial conformation. Some of the decomposition reactions involved the release of low-molecular-weight products. Excluding radicals, the most commonly observed species were glycolaldehyde, water, formaldehyde and formic acid. Many of our observations are supported by the existing experimental and theoretical knowledge. We did not, however, observe the formation of levoglucosan, which is the dominant product in conventional pyrolysis experiments at much lower temperatures. This is understandable, since the high temperatures can force the dominance of radical reactions over pericyclic reactions. Nevertheless, our results support further use of ReaxFF-based molecular dynamics simulations in the study of cellulose pyrolysis.

show abstract

Section: Discussionmentioning

confidence: 99%

High-temperature decomposition of the cellulose molecule: a stochastic molecular dynamics study

Paajanen

Vaari

2017

Cellulose

View full text Add to dashboard Cite

show abstract

“…The total elapsed simulation time is summed from contributions of each replica, where such parallelisation is indistinguishable from an analogous single-processor simulation if the transition process follows first-order escape kinetics, as demonstrated in the original PRD publication. 125 Joshi et al 126 implemented PRD with the ReaxFF potential, where a state-transition event was defined as a change in molecular connectivity (i.e., a chemical reaction). When implemented with 180 replicas to track the thermal pyrolysis of n-heptane, PRD-ReaxFF was able to reach simulation times on the order of 1 μs with a parallel scaling efficiency of 93% (Figure 5b) aARRDyn, introduced to ReaxFF by Cheng et al, 127 employs a 'bond boost' algorithm to accelerate dynamic evolution across the potential energy surface.…”

Section: Recently Developed Methodsmentioning

confidence: 99%

The ReaxFF reactive force-field: development, applications and future directions

et al. 2016

View full text Add to dashboard Cite

The reactive force-field (ReaxFF) interatomic potential is a powerful computational tool for exploring, developing and optimizing material properties. Methods based on the principles of quantum mechanics (QM), while offering valuable theoretical guidance at the electronic level, are often too computationally intense for simulations that consider the full dynamic evolution of a system. Alternatively, empirical interatomic potentials that are based on classical principles require significantly fewer computational resources, which enables simulations to better describe dynamic processes over longer timeframes and on larger scales. Such methods, however, typically require a predefined connectivity between atoms, precluding simulations that involve reactive events. The ReaxFF method was developed to help bridge this gap. Approaching the gap from the classical side, ReaxFF casts the empirical interatomic potential within a bond-order formalism, thus implicitly describing chemical bonding without expensive QM calculations. This article provides an overview of the development, application, and future directions of the ReaxFF method. INTRODUCTIONAtomistic-scale computational techniques provide a powerful means for exploring, developing and optimizing promising properties of novel materials. Simulation methods based on quantum mechanics (QM) have grown in popularity over recent decades due to the development of user-friendly software packages making QM level calculations widely accessible. Such availability has proved particularly relevant to material design, where QM frequently serves as a theoretical guide and screening tool. Unfortunately, the computational cost inherent to QM level calculations severely limits simulation scales. This limitation often excludes QM methods from considering the dynamic evolution of a system, thus hampering our theoretical understanding of key factors affecting the overall behaviour of a material. To alleviate this issue, QM structure and energy data are used to train empirical force fields that require significantly fewer computational resources, thereby enabling simulations to better describe dynamic processes. Such empirical methods, including reactive force-field (ReaxFF), 1 trade accuracy for lower computational expense, making it possible to reach simulation scales that are orders of magnitude beyond what is tractable for QM.Atomistic force-field methods utilise empirically determined interatomic potentials to calculate system energy as a function of atomic positions. Classical approximations are well suited for nonreactive interactions, such as angle-strain represented by harmonic potentials, dispersion represented by van der Waals potentials and Coulombic interactions represented by various polarisation schemes. However, such descriptions are inadequate for modelling changes in atom connectivity (i.e., for modelling chemical reactions as bonds break and form). This motivates the

show abstract

“…Kissin reviewed in 2001 possible reaction mechanisms and stated that although the mechanism of catalytic cracking is based on carbenium ions and might at first sight seem relatively simple, many issues and questions remain. 267,268 Fig. 262 A. Adsorption of alkanes in zeolites.…”

Section: View Article Onlinementioning

confidence: 99%

Advances in theory and their application within the field of zeolite chemistry

et al. 2015

View full text Add to dashboard Cite

Zeolites are versatile and fascinating materials which are vital for a wide range of industries, due to their unique structural and chemical properties, which are the basis of applications in gas separation, ion exchange and catalysis. Given their economic impact, there is a powerful incentive for smart design of new materials with enhanced functionalities to obtain the best material for a given application. Over the last decades, theoretical modeling has matured to a level that model guided design has become within reach. Major hurdles have been overcome to reach this point and almost all contemporary methods in computational materials chemistry are actively used in the field of modeling zeolite chemistry and applications. Integration of complementary modeling approaches is necessary to obtain reliable predictions and rationalizations from theory. A close synergy between experimentalists and theoreticians has led to a deep understanding of the complexity of the system at hand, but also allowed the identification of shortcomings in current theoretical approaches. Inspired by the importance of zeolite characterization which can now be performed at the single atom and single molecule level from experiment, computational spectroscopy has grown in importance in the last decade. In this review most of the currently available modeling tools are introduced and illustrated on the most challenging problems in zeolite science. Directions for future model developments will be given.

show abstract

Connectivity-Based Parallel Replica Dynamics for Chemically Reactive Systems: From Femtoseconds to Microseconds

Cited by 57 publications

References 32 publications

High-temperature decomposition of the cellulose molecule: a stochastic molecular dynamics study

High-temperature decomposition of the cellulose molecule: a stochastic molecular dynamics study

The ReaxFF reactive force-field: development, applications and future directions

Advances in theory and their application within the field of zeolite chemistry

Contact Info

Product

Resources

About