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This paper presents a holistic view of the structural phase transitions in nanocrystals. The databases for size-induced phase transitions is a main part of this paper. The database on transitions with temperature contains 603 items on 415 crystals, and database on transitions under high pressure contains 209 items in 124 crystals. Moreover, some new aspects of such transitions are presented like island diagram and new analysis of anomalous compressibility observed in some nanocrystals. [ABSTRACT FROM AUTHOR]

The new form of the phase diagram is proposed for nanocrystals. This island diagram shows the regions of the calcination temperature required to obtain the nanocrystals of given range of crystallite size. This explains why the temperature-induced phase transitions are not possible in some crystals. However, the change of crystallite size can induce the phase transition. [ABSTRACT FROM AUTHOR]

I would like to comment the crystallographic part of the paper by Santosh Kumor Parida and Rama Narayan Prasad Choudhary entitled 'Preparation method and cerium dopant effects on the properties of BaMnO3 single perovskite' and published in 'Phase Transitions' in September 2020 [1]. There are several errors that should be corrected, if possible. [ABSTRACT FROM AUTHOR]

The literature data on the smallest unit cells as well as on the smallest single crystals studied by X-ray diffraction are reviewed. Different types of phase diagrams “temperature—grain size” are presented and discussed. The literature data on the grain-size driven structural phase transitions occurring in nanocrystals (quantum dots) are presented in the form of a database. It was found that there were no reports on phase transitions occurring for nanocrystalline grains with a linear dimension smaller than 7 unit cells. The grain-size driven phase transitions for some nanocrystalline double tungstates, molybdates and phosphates are also described. [ABSTRACT FROM AUTHOR]

Highlights • Several errors were found and corrected. • All corrections concern the crystallographic part of paper. • Due to the overlapping of Bragg peaks the crystallite size is not correctly calculated. Abstract The commented paper presents the results on structural and optical studies on the nanocrystals of SrAl2O4:Eu. Unfortunately, there are mistakes in the analysis of diffraction patterns in this paper which should be corrected to avoid its use in the future papers by Authors and by other people. [ABSTRACT FROM AUTHOR]

Highlights • Several errors were found and corrected. • Some not correct statements were explained. • All corrections concerns the crystallographic part of paper. [ABSTRACT FROM AUTHOR]

Abstract: Well-crystallized MnWO4 nanoparticles with 20–100nm sizes were synthesized by a mild hydrothermal crystallization process. X-ray diffraction and TEM results show that particles have tendency to grow in a shape of nanorods elongated in the c direction. They also show that the particles synthesized from MnCl2 have smaller concentration of defects than those synthesized from MnSO4·H2O. Raman spectra revealed weak changes with decreasing particle size due to phonon confinement effect and defects. In contrast to this behavior, IR spectra showed much more pronounced changes. Origin of this behavior is discussed. Raman and IR spectra showed also presence of additional bands at 923 and 914cm−1, respectively. These bands have been attributed to presence of terminal Wt the surface of MnWO4 nanocrystallites. Specific heat and magnetization studies revealed broad anomalies at 11.0–11.4K, which correspond to the two magnetic transitions found for bulk MnWO4 at 12.5 and 13.5K. [Copyright &y& Elsevier]