Possibilities of Neural Network Powder Diffraction Analysis Crystal Structure of Chemical Compounds

Some possibilities of using convolutional artificial neural networks (ANN) for powder diffraction structural analysis of crystalline substances have been investigated. First, ANNs are used to classify crystalline systems and space groups according to calculated full-profile diffractograms calculated from the crystal structures of the ICSD database (2017 year). The ICSD database contains 192004 structures, of which 80% was used for in-depth network training, and 20% for independent testing of recognition accuracy. The accuracy of classification by a network of crystalline systems was 87.9%, and that of space groups was 77.2%. Secondly, the ANN is used for a similar classification of structural models generated by the stochastic genetic algorithm in the search processes for triclinic crystal structures of test compound K4SnO4 according to their full-profile diffraction patterns. The classification criterion was the entry of one or several atoms into their crystallographic positions in the structure of a substance. Independent deep network training was performed on 120 thousand structural models of the K4PbO4 triclinic structure generated in several runs of the genetic algorithm. The accuracy of the classification of K4SnO4 structural models exceeded 50%. The results show that deeply trained convolutional ANNs can be effective for classifying crystal structures according to the structural characteristics of their powder diffraction patterns

An accurate determination of cryolite ratio in industrial aluminum baths by wavelength-dispersive X-ray fluorescence spectrometry

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.The efficiency of aluminum smelting cells relies on control in maintaining different cell's parameters, including bath chemistry. In industry, X-ray diffraction analysis is normally used to control the primary characteristic of bath chemistry, namely cryolite ratio. However, from 2 to 3% of all the results contain over-normative errors, and this declines the efficiency of the process control and the overall smelting efficiency. Present paper provides a wavelength-dispersive X-ray fluorescence spectrometric methodology for measuring cryolite ratio of aluminum bath in detail. It guarantees measuring cryolite ratio with the accuracy of 0.04, which is required by the smelting technology. The methodology includes the calibration of a wavelength X-ray fluorescence spectrometer with reference materials, the measurement of concentrations of F, Na, Al, Ca and Mg, and the calculation of cryolite ratio from the measured concentrations. We evaluated two possible strategies of measuring cryolite ratio by X-ray fluorescence. The one that does not involve oxygen quantification provides the technologically required accuracy of cryolite ratio measurements. Also, new results of implementing the methodology in the process control at Krasnoyarsk aluminum smelter are provided. The combined process control of cryolite ratio by X-ray diffraction and X-ray fluorescence ensures accurate and reliable results, eliminates gross analytical errors and stabilizes overall performance of a smelter's process control system. Thus, use of X-ray fluorescence analysis for measuring CR contributes in stable current yield of aluminum

System NaF-KF-AlF₃: Solid Solutions Based on the Сhiolite Structure

Методом рентгеновской дифракции на экспериментально полученных образцах изучено образование твердых растворов в субсолидусной области системы NaF-KF-AlF₃. Впервые установлено образование твердых растворов на основе структуры хиолита c составом (Na(5-x)Kx)Al₃F₁₄, 0<x<0,4). Изменение параметров кристаллической решетки хиолита осуществляется в диапазоне от 7,010(3) до 7,050(3) Å и от 10,365(10) до 10,400(10) Å. Уточнением кристаллической структуры установлено, что замещение натрия на калий происходит только в 2-кратной позиции натрия на величину ~ 40 %. Предельное растворение в хиолите не превышает 5 % (мас.) KF. Твердый раствор устойчив в диапазоне от температуры плавления до комнатнойThe formation of solid solutions in the NaF-KF-AlF₃ system has been studied by X-ray diffraction on samples obtained experimentally. For the first time the formation of solid solutions based on structure of chiolite with the composition (Na(5-x)Kx)Al₃F₁₄ , 0 < x < 0,4) has been established. The change of a crystal lattice of chiolite occurs in the range: (a) – from 7,010 (3) to 7,050 (3) Å, (c) from 10,365 (10) Å to 10,400 (10) Å. The sodium potassium substitution occurs at only a 2-fold sodium position by an amount ~ 40 % established by refinement of the crystal structure. The limit dissolution of chiolite in less than 5 % (wt.) KF. The solid solution is stable in the range from the melting temperature to the roo

Possibilities of Neural Network Powder Diffraction Analysis Crystal Structure of Chemical Compounds

Исследованы некоторые возможности применения сверточных искусственных нейронных сетей (ИНС) для порошкового дифракционного структурного анализа кристаллических веществ. Во-первых, ИНС применены для классификации кристаллических систем и пространственных групп симметрии по расчетным полнопрофильным дифрактограммам, вычисленным из кристаллических структур базы данных ICSD 2017 г. База ICSD содержит 192004 структуры, из которых 80 % использовалось для глубокого обучения сети, а 20 % для независимого тестирования точности распознавания. Точность классификации сетью кристаллических систем составила 87,9 %, а пространственных групп – 77,2 %. Во- вторых, другая ИНС применена для классификации структурных моделей, сгенерированных стохастическим генетическим алгоритмом в процессах поиска кристаллических структур тестовых триклинных соединений K4SnO4 и K4SnO4, по их полнопрофильным дифрактограммам. Было сгенерировано около 150 тысяч структурных моделей каждой из этих структур. Глубокое обучение сети выполнялось на дифрактограммах структурных моделей K4PbO4. Обученная сеть была применена для классификации структурных моделей K4SnO4 по их дифрактограммам. Критерием классификации являлось попадание атомов в их кристаллографические позиции в структуре. Точность классификации адекватных позиций атомов в структурных моделях K4SnO4 превысила 50 %.Some possibilities of using convolutional artificial neural networks (ANN) for powder diffraction structural analysis of crystalline substances have been investigated. First, ANNs are used to classify crystalline systems and space groups according to calculated full-profile diffractograms calculated from the crystal structures of the ICSD database (2017 year). The ICSD database contains 192004 structures, of which 80% was used for in-depth network training, and 20% for independent testing of recognition accuracy. The accuracy of classification by a network of crystalline systems was 87.9%, and that of space groups was 77.2%. Secondly, the ANN is used for a similar classification of structural models generated by the stochastic genetic algorithm in the search processes for triclinic crystal structures of test compound K4SnO4 according to their full-profile diffraction patterns. The classification criterion was the entry of one or several atoms into their crystallographic positions in the structure of a substance. Independent deep network training was performed on 120 thousand structural models of the K4PbO4 triclinic structure generated in several runs of the genetic algorithm. The accuracy of the classification of K4SnO4 structural models exceeded 50%. The results show that deeply trained convolutional ANNs can be effective for classifying crystal structures according to the structural characteristics of their powder diffraction pattern

System NaF-KF-AlF₃: Solid Solutions Based on the Сhiolite Structure

Методом рентгеновской дифракции на экспериментально полученных образцах изучено образование твердых растворов в субсолидусной области системы NaF-KF-AlF₃. Впервые установлено образование твердых растворов на основе структуры хиолита c составом (Na(5-x)Kx)Al₃F₁₄, 0<x<0,4). Изменение параметров кристаллической решетки хиолита осуществляется в диапазоне от 7,010(3) до 7,050(3) Å и от 10,365(10) до 10,400(10) Å. Уточнением кристаллической структуры установлено, что замещение натрия на калий происходит только в 2-кратной позиции натрия на величину ~ 40 %. Предельное растворение в хиолите не превышает 5 % (мас.) KF. Твердый раствор устойчив в диапазоне от температуры плавления до комнатнойThe formation of solid solutions in the NaF-KF-AlF₃ system has been studied by X-ray diffraction on samples obtained experimentally. For the first time the formation of solid solutions based on structure of chiolite with the composition (Na(5-x)Kx)Al₃F₁₄ , 0 < x < 0,4) has been established. The change of a crystal lattice of chiolite occurs in the range: (a) – from 7,010 (3) to 7,050 (3) Å, (c) from 10,365 (10) Å to 10,400 (10) Å. The sodium potassium substitution occurs at only a 2-fold sodium position by an amount ~ 40 % established by refinement of the crystal structure. The limit dissolution of chiolite in less than 5 % (wt.) KF. The solid solution is stable in the range from the melting temperature to the roo

Твердые растворы в алюминиевых электролитах с участием LiF

The paper presents the investigation of the solid solutions formation in the fluoride system Na5Al3F14-Na3AlF6-K3AlF6 with the addition of LiF. Two local regions were under consideration. The first case concerns the possibility of potassium and sodium cations replacing with lithium in the elpasolite (K2NaAlF6) when LiF is added to the electrolyte. In the second, the effect of lithium fluoride on the chiolite (Na5Al3F14) was studied. The investigation was motivated by the need to control the composition of the electrolyte during the electrolytic production of aluminum. The electrolyte samples were obtained from the initial fluorides under laboratory conditions. Determination of crystal-chemical details of the structure of solid solutions was carried out by the method of full-profile analysis (Rietveld method) on multiphase polycrystalline samples. It was found that the addition of LiF in the structure of elpasolite is accompanied by a gradual substitution of lithium for sodium with the formation, ultimately, of the K2LiAlF6 phase with the lattice parameter a = 8.0779 Å. Potassium is not subject to substitution. No dissolution of LiF in the structure of cryolite (Na3AlF6) was found. It was shown that chiolite does not form solid solutions with LiF upon crystallizationПредставлены исследования образования твердых растворов в двух локальных областях системы Na5Al3F14-Na3AlF6-K3AlF6 с добавлением LiF. В первом случае рассмотрена возможность замещения катионов калия и натрия в эльпасолите (K2NaAlF6) на литий при добавлении в электролит LiF. Во втором изучено влияние фторида лития на хиолит (Na5Al3F14). Изучение фторидной системы обосновано необходимостью контроля состава электролита при электролизе алюминия. Исследования были выполнены на образцах, полученных из исходных фторидов в лабораторных условиях. Определение кристаллохимических деталей строения твердых растворов проведено методом полнопрофильного анализа (метод Ритвельда) на многофазных поликристаллических образцах. Установлено, что при добавлении LiF в структуре эльпасолита происходит постепенное замещение натрия на литий с образованием в конечном счете фазы K2LiAlF6 с параметром решетки а=8,0779 Å. Калий не подвергается замещению. Растворения LiF в структуре криолита (Na3AlF6) не обнаружено. Показано, что хиолит при кристаллизации не образует твердых растворов с Li