Dielectric properties of pyridine–ethanol mixtures: density functional theory and experiments

Int J of Quantum Chemistry

Glezakou

2020

Chemical clusters are relevant to many applications in catalysis, separations, materials, and energy sciences. Experimentally, the structure of clusters is difficult to determine, but it is very important in understanding their chemistry and properties. Computational methods can be used to examine cluster structure, however finding the most stable structure is not simple, particularly as the cluster size increases. Global optimization techniques have long been used to tackle the problem of the most stable structure, but such approaches would have to look for a global minimum, while sampling local minima over the whole potential energy surface as well. In this review, the state‐of‐the‐art theory of global optimization theory is summarized. First, the definition, significance, relation to experiments, and a brief history of global optimization is presented. We then discuss, in more detail, three versatile global optimization methods: the basin hopping, the artificial bee colony algorithm, and the genetic algorithm. We close with some representative application examples of global optimization of clusters since 2016 and the challenges, open questions and opportunities in this field.

Section: Applicationsmentioning

confidence: 99%

Global optimization of chemical cluster structures: Methods, applications, and challenges

Int J of Quantum Chemistry

Glezakou

2020

“…We adapted the algorithm for chemical problems and wrapped it in a program called ABCluster. , Since then, ABCluster has gained wide applications in chemical problems from different fields. One example is that ABCluster was used to search the GMs of lanthanide (Ln) doped silicon cluster anions as large as LnSi 20 – , and the calculated photoelectron spectroscopy from these GMs agrees well with the experimental ones. − Another example is that several authors searched the GMs of clusters consisting of atmosphere related molecules like water, ammonia, nitric acid, hydroxymethanesulfonic acid, sulfuric anhydride, and pentoxide–iodic acid. − Using GMs of different sizes, atmospheric cluster dynamics equations can be solved, and a number of atmospheric chemical phenomena were successfully explained. − ABCluster was also applied in catalysis, ,− materials science, − solution chemistry, − etc. Therefore, the ABC algorithm is proven to be a highly successful method for searching GMs of atomic and molecular clusters to solve realistic chemical problems.…”

Section: Introductionmentioning

confidence: 98%

“…[58][59][60][61][62][63][64][65][66][67][68][69][70] Using GMs of different sizes, atmospheric cluster dynamics equations can be solved 71 and a lot of atmospheric chemical phenomena were successfully explained. [58][59][60][61][62][63][64][65][66][67][68][69][70] ABCluster was also applied in catalysis, 4,[72][73][74] material science, [75][76][77] solution chemistry, [78][79][80] etc. Therefore, the ABC algorithm is proven to be a highly successful method for searching GMs of atomic and molecular clusters to solve realistic chemical problems.…”

Section: Introductionmentioning

confidence: 99%

NWPEsSe: An Adaptive-Learning Global Optimization Algorithm for Nanosized Cluster Systems

J. Chem. Theory Comput.

Glezakou

Rousseau

et al. 2020

Global optimization constitutes an important and fundamental problem in theoretical studies in many chemical fields, such as catalysis, materials or separations problems. In this paper, a novel algorithm has been developed for the global optimization of large systems including neat and ligated clusters in gas phase, and supported clusters in periodic boundary conditions. The method is based on an updated artificial bee colony (ABC) algorithm method, that allows for adaptive-learning during the search process. The new algorithm is tested against four classes of systems of diverse chemical nature: gas phase Au 55 , ligated Au 8 2+ , Au 8 supported on graphene oxide and defected rutile, and a large cluster assembly [Co 6 Te 8 (PEt 3 ) 6 ][C 60 ] , with sizes ranging between 1 to 3 nm and containing up to 1300 atoms. Reliable global minima (GMs) are obtained for all cases, either confirming published data or reporting new lower energy structures. The algorithm and interface to other codes in the form of an independent program, Northwest Potential Energy Search Engine (NWPEsSe), is freely available and it provides a powerful and efficient approach for global optimization of nanosized cluster systems.

“…One can also observe that the estimation of dielectric properties of single reagent is better than that of reagent mixtures. Researchers reported that the conventional mixture formulas cannot describe the dielectric property of mixed reagents appropriately, since the mixture may present an anomaly in its dielectric property [ 38 , 39 ]. There may be also an anomaly in the mixtures measured in the paper, causing the difference between the measured and calculated data of mixtures.…”

Section: Measured Results and Discussionmentioning

confidence: 99%

An On-Line System for High Temperature Dielectric Property Measurement of Microwave-Assisted Sintering Materials

Wang

et al. 2019

Materials

Self Cite

Microwave-assisted sintering materials have been proven to deliver improvements in the mechanical and physicochemical properties of the materials, compared with conventional sintering methods. Accurate values of dielectric properties of materials under high temperatures are essential for microwave-assisted sintering. In view of this, this paper, proposes an on-line system to measure the high temperature dielectric properties of materials under microwave processing at a frequency of 2450 MHz. A custom-designed ridge waveguide is utilized, where samples are heated and measured simultaneously. An artificial neural network (ANN) trained with the corresponding simulation data is integrated into this system to reverse the permittivity of the measured materials. This whole system is tested at room temperature with different materials. Accuracies of measuring dielectric property with an error lower than 9% with respect to theoretical data have been achieved even for high loss media. The functionality of the dielectric measurement system has also been demonstrated by heating and measuring Macor and Duran ceramic glass samples up to 800 °C. All the preliminary experiments prove the feasibility of this system. It provides another method for dielectric property measurement and improves the understanding of the mechanism between microwave and media under high temperatures, which is helpful for optimizing the microwave-assisted sintering of materials.