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Crystals
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Polymorphism in Crystals
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Polymorphism in Crystals

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystal Engineering".

Deadline for manuscript submissions: closed (20 February 2023) | Viewed by 25435

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Dr. Jingxiang Yang

E-Mail Website
Guest Editor
State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China
Interests: polymorph; pesticide; crystal engineering
Dr. Xin Huang

E-Mail Website
Guest Editor
National Engineering Research Center of Industrial Crystallization Technology, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
Interests: polymorph; crystal engineering; functional crystal material
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Polymorphism, the property of a compound to crystallize in more than one distinct crystal form, plays an indispensable role in researching and developing pharmaceuticals, agrochemicals, materials, and food. Polymorphs exhibit different properties, such as crystal habit, solubility, dissolution rate, melting point, stability, mechanical properties, even bioavailability, which may influence product quality. Therefore, the study on polymorphs’ behavior can provide a theoretical basis for selecting optimal solid forms and serve for the polymorphic control and optimization of products as a primary method. Recently, significant progress has been made in the experimental discovery and theoretical prediction of crystal polymorphs. A large quantity of molecules have been discovered to have polymorphs that are mainly attributed to the molecule’s conformational flexibility and the existence of various functionalities in the molecule that could act as hydrogen bond donor/acceptor.  In addition to conventional solution crystallization, more polymorphisms have been found in the melt, in confinement, and in the presence of ultrasound/lasers.

Moreover, computational predictions usually yield far more possible polymorphs than are known. The ultimate limitations of experimental reachable polymorphs and thermodynamical and structure–activity relationships of the polymorphs remain an open question. The present Special Issue on “Polymorphism in Crystals” invites status reports summarizing the progress achieved in recent years.

Dr. Jingxiang Yang
Prof. Dr. Xin Huang
Guest Editors

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

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Published Papers (13 papers)

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Research

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13 pages, 15914 KiB  
Article
The Influence of Different Types of SiO2 Precursors and Ag Addition on the Structure of Selected Titania-Silica Gels
by Anna Adamczyk
Crystals 2023, 13(5), 811; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst13050811 - 13 May 2023
Cited by 2 | Viewed by 946
Abstract
In this paper, samples of titania-silica system were obtained by the sol-gel method as bulk materials, using titanium propoxide Ti(C3H7O)4 to introduce titania and two precursors of SiO2: TEOS tetraethoxysilane Si(OC2H5)4 [...] Read more.
In this paper, samples of titania-silica system were obtained by the sol-gel method as bulk materials, using titanium propoxide Ti(C3H7O)4 to introduce titania and two precursors of SiO2: TEOS tetraethoxysilane Si(OC2H5)4 and DDS dimethyldiethoxysilane (CH3)2(C2H5O)2Si. To enhance antibacterial properties, Ag was added to gels of selected compositions. The main aim of the performed studies was to find the correlations between the structural changes and the applied precursor of silica. Simultaneously, the influence of different compositions of gels and the addition of Ag on the specimens’ structure was investigated. To study the structure, two complementary methods, FTIR (Fourier Transform InfraRed) spectroscopy and X-ray diffraction, were applied. The analysis of the FTIR spectra and the XRD patterns made it possible to confirm the amorphous state of all dried gels and establish the presence of TiO2 polymorphs: anatase and rutile in all annealed samples. The addition of Ag atoms into the gels caused the crystallization of cristobalite phase in addition to titania polymorphs. The presence of crystalline Ag phase in the annealed gels allowed the calculation dimensions of Ag crystallites based on the Scherrer equation. The use of DDS as a silica precursor led to easier and faster crystallization of different TiO2 phases in the annealed samples and parallel increases in the depolymerization of silica lattice. Full article
(This article belongs to the Special Issue Polymorphism in Crystals)
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15 pages, 6339 KiB  
Article
Enhancing the Water Solubility of 9-Fluorenone Using Cyclodextrin Inclusions: A Green Approach for the Environmental Remediation of OPAHs
by Yue Niu, Ling Zhou, Huiqi Wang, Jiayu Dai, Ying Bao, Baohong Hou and Qiuxiang Yin
Crystals 2023, 13(5), 775; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst13050775 - 06 May 2023
Cited by 1 | Viewed by 1046
Abstract
Oxygenated polycyclic aromatic hydrocarbons (OPAHs) are toxic and carcinogenic compounds widely present in the natural environment, posing a serious threat to the environment and human health. However, the removal of OPAHs is mainly hindered by their low water solubility. Cyclodextrins (CDs) are frequently [...] Read more.
Oxygenated polycyclic aromatic hydrocarbons (OPAHs) are toxic and carcinogenic compounds widely present in the natural environment, posing a serious threat to the environment and human health. However, the removal of OPAHs is mainly hindered by their low water solubility. Cyclodextrins (CDs) are frequently used to form inclusion complexes (ICs) with hydrophobic molecules to improve their solubility. In this study, we investigated the solubility enhancement ability of different CDs on 9-fluorenone, a common OPAH, through phase solubility experiments. We successfully prepared three solid ICs of 9-fluorenone with β-, hydroxypropyl-β-(HP-β-) and sulfobutylether-β-CD (SBE-β-CD) using the cooling crystallization method for the first time and characterized them via powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, etc. Molecular dynamics simulations were employed to investigate the binding modes and stable configurations of the ICs in the liquid phase and to explore the factors affecting their solubility enhancement ability. The results showed that all the CDs had a solubility enhancement effect on 9-fluorenone, with SBE-β-CD displaying the strongest effect, increasing the solubility of 9-fluorenone by 146 times. HP-β-CD, β-CD, α-CD, and γ-CD followed in decreasing order. Moreover, 9-fluorenone formed a ratio of 1:1 ICs to CDs. In addition, the interaction energy between SBE-β-CD and 9-fluorenone was the lowest among the CDs, which further validated the results of the phase solubility experiments from a theoretical perspective. Overall, this study provides a green method for the removal of 9-fluorenone pollutants in the environment and is expected to be applied to the removal and environmental remediation of other OPAHs. Full article
(This article belongs to the Special Issue Polymorphism in Crystals)
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Graphical abstract

11 pages, 3422 KiB  
Article
Silica Nanoparticles-Induced Lysozyme Crystallization: Effects of Particle Sizes
by Yuxiao Zhang, Xuntao Jiang, Xia Wu, Xiaoqiang Wang, Fang Huang, Kefei Li, Gaoyang Zheng, Shengzhou Lu, Yanxu Ma, Yuyu Zhou and Xiaoxi Yu
Crystals 2022, 12(11), 1623; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12111623 - 12 Nov 2022
Cited by 2 | Viewed by 1304
Abstract
This study aimed to explore the effects of nucleate agent sizes on lysozyme crystallization. Silica nanoparticles (SNP) with four different particle sizes of 5 nm, 15 nm, 50 nm, and 100 nm were chosen for investigation. Studies were carried out both microscopically and [...] Read more.
This study aimed to explore the effects of nucleate agent sizes on lysozyme crystallization. Silica nanoparticles (SNP) with four different particle sizes of 5 nm, 15 nm, 50 nm, and 100 nm were chosen for investigation. Studies were carried out both microscopically and macroscopically. After adding SNP, the morphological defects of lysozyme crystals decreased, and the number of crystals increases with the size of the SNP. The interaction between SNP and lysozyme was further explored using UV spectroscopy, fluorescence spectroscopy, and Zeta potential. It was found that the interaction between SNP and lysozyme was mainly electrostatic interaction, which increased with the size of SNP. As a result, lysozyme could be attracted to the surface of SNP and aggregated to form the nucleus. Finally, the activity test and circular dichroism showed that SNP had little effect on protein secondary structure. Full article
(This article belongs to the Special Issue Polymorphism in Crystals)
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11 pages, 11722 KiB  
Article
Electroextraction of Ytterbium on the Liquid Lead Cathode in LiCl-KCl Eutectic
by Zhuyao Li, Liandi Zhu, Dandan Tang, Ying Dai, Feiqiang He, Zhi Gao, Cheng Liu, Hui Liu, Limin Zhou, Zhirong Liu and Jinbo Ouyang
Crystals 2022, 12(10), 1453; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12101453 - 14 Oct 2022
Cited by 1 | Viewed by 1357
Abstract
The reduction mechanisms of Yb(III) on W electrodes in molten LiCl-KCl-YbCl3 were explored at 773 K, and the diffusion coefficient of Yb(III) was determined. Then, various electrochemical techniques were employed to investigate the electroreduction of Yb(III) in molten LiCl-KCl on a liquid [...] Read more.
The reduction mechanisms of Yb(III) on W electrodes in molten LiCl-KCl-YbCl3 were explored at 773 K, and the diffusion coefficient of Yb(III) was determined. Then, various electrochemical techniques were employed to investigate the electroreduction of Yb(III) in molten LiCl-KCl on a liquid Pb film and Pb electrode. Electrochemical signals were associated with forming Pb3Yb, PbYb, Pb3Yb5, and PbYb2. The deposition potentials and equilibrium potentials of four Pb-Yb intermetallics were obtained through open-circuit chronopotentiometry. Metallic Yb was extracted by potentiostatic electrolysis (PE) on a liquid Pb electrode, and XRD analyzed the Pb-Yb alloy obtained at different extraction times. The recovered Yb was found in the form of Pb3Yb and PbYb intermetallics. The extraction efficiency of Yb was calculated according to ICP analysis results, and extraction effectivity could attain 94.5% via PE at −1.86 V for 14 h. Full article
(This article belongs to the Special Issue Polymorphism in Crystals)
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14 pages, 9933 KiB  
Article
Study on Precipitation Processes and Phase Transformation Kinetics of Iron Phosphate Dihydrate
by Huiqi Wang, Mingxia Guo, Yue Niu, Jiayu Dai, Qiuxiang Yin and Ling Zhou
Crystals 2022, 12(10), 1369; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12101369 - 27 Sep 2022
Cited by 2 | Viewed by 1816
Abstract
The process of the phase transformation from amorphous to crystalline FePO4·2H2O was studied in this research. It was found that Fe and P are predominantly present as FeHPO4+ and FeH2PO42+ and an induction [...] Read more.
The process of the phase transformation from amorphous to crystalline FePO4·2H2O was studied in this research. It was found that Fe and P are predominantly present as FeHPO4+ and FeH2PO42+ and an induction period exists during the transition from amorphous to monoclinic form. The induction period and the time required for phase transformation were shortened with the increased temperature. Phase transformation could be kinetically described by the Johnson–Mehl–Avrami (JMA) dynamics model. The dissolution rate of amorphous FePO4·2H2O is the rate-limiting step of this process. the activation energy of phase transformation is calculated to be 9.619 kJ/mol. The results in this study provided more guidelines for the regulation of FePO4·2H2O precursors by precipitation method. Full article
(This article belongs to the Special Issue Polymorphism in Crystals)
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25 pages, 4243 KiB  
Article
Croconic Acid Doped Glycine Single Crystals: Growth, Crystal Structure, UV-Vis, FTIR, Raman and Photoluminescence Spectroscopy
by Elena Balashova, Aleksandr A. Levin, Valery Davydov, Alexander Smirnov, Anatoly Starukhin, Sergey Pavlov, Boris Krichevtsov, Andrey Zolotarev, Hongjun Zhang, Fangzhe Li and Hua Ke
Crystals 2022, 12(10), 1342; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12101342 - 22 Sep 2022
Cited by 2 | Viewed by 1643
Abstract
Glycine (Gly) single crystals doped with croconic acid (CA) were grown by evaporation from aqueous solutions. Depending on the weight ratio of Gly and CA in solutions, the crystals take on a plate or pyramidal shape. Both powder and single crystal XRD analyses [...] Read more.
Glycine (Gly) single crystals doped with croconic acid (CA) were grown by evaporation from aqueous solutions. Depending on the weight ratio of Gly and CA in solutions, the crystals take on a plate or pyramidal shape. Both powder and single crystal XRD analyses indicate that the crystal lattices of plates (α-Gly:CA) and pyramides (γ-Gly:CA) correspond to the lattices of pure α-Gly and γ-Gly polymorphs, respectively. Raman and FTIR spectra of Gly:CA crystals are very close to the spectra of undoped crystals, but include bands associated with CA impurity. Analysis of UV-Vis absorption spectra indicates that doping does not remarkably change bandgap value Eg~5.2 eV but results in appearance of strong absorption bands in the transparency region of pure glycine crystals, which result from local electronic transitions. Incorporation of CA molecules in Gly creates strong green photoluminescence in a wide spectral range 1.6–3.6 eV. Comparison of the optical spectra of Gly:CA and previously studied TGS:CA crystals indicates that in both cases, the modifications of the optical spectra induced by CA doping are practically identical and are related to the interaction between CA molecules located in the pores of the host Gly crystals and neighboring Gly molecules. Full article
(This article belongs to the Special Issue Polymorphism in Crystals)
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12 pages, 5696 KiB  
Article
Solution-Mediated Polymorphic Transformation of L-Carnosine from Form II to Form I
by Yanan Zhou, Shuyi Zong, Jie Gao, Chunsong Liu and Ting Wang
Crystals 2022, 12(7), 1014; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12071014 - 21 Jul 2022
Cited by 2 | Viewed by 1456
Abstract
In this study, L-carnosine was chosen as the model compound to systematically study solution-mediated polymorphic transformation by online experiment and theoretical simulation. Form II, a new polymorph of L-carnosine, was developed using an antisolvent crystallization method. The properties of form I and form [...] Read more.
In this study, L-carnosine was chosen as the model compound to systematically study solution-mediated polymorphic transformation by online experiment and theoretical simulation. Form II, a new polymorph of L-carnosine, was developed using an antisolvent crystallization method. The properties of form I and form II L-carnosine were characterized by powder X-ray diffraction, polarizing microscope, thermal analysis, and Raman spectroscopy. In order to explore the relative stability, the solubility of L-carnosine form I and form II in a (water + DMAC) binary solvent mixture was determined by a dynamic method. During the solution-mediated polymorphic transformation process of L-carnosine in different solvents, Raman spectroscopy was employed to detect the solid-phase composition of suspension in situ, and the gravimetric method was used to measure the liquid concentration. In addition, the effect of the solvent on the transformation process was evaluated and analyzed. Finally, a mathematical model of dissolution–precipitation was established to simulate the kinetics of the polymorphic transformation process based on the experimental data. Taking the simulation results and the experimental data into consideration, the controlling step of solution-mediated polymorphic transformation was discussed. Full article
(This article belongs to the Special Issue Polymorphism in Crystals)
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21 pages, 3897 KiB  
Article
Thermodynamic Properties of 1,5-Pentanediamine Adipate Dihydrate in Three Binary Solvent Systems from 278.15 K to 313.15 K
by Liang Li, Yihan Zhao, Baohong Hou, Han Feng, Na Wang, Dong Liu, Yingjie Ma, Ting Wang and Hongxun Hao
Crystals 2022, 12(6), 877; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12060877 - 20 Jun 2022
Cited by 1 | Viewed by 1390
Abstract
In this work, solubility data of 1,5-pentanediamine adipate dihydrate in binary solvent systems of water + methanol, water + ethanol and water + N,N-dimethylformamide were experimentally measured via a static gravimetric method in the temperature range from 278.15 K to 313.15 K under [...] Read more.
In this work, solubility data of 1,5-pentanediamine adipate dihydrate in binary solvent systems of water + methanol, water + ethanol and water + N,N-dimethylformamide were experimentally measured via a static gravimetric method in the temperature range from 278.15 K to 313.15 K under atmospheric pressure. The results indicated that the solubility of 1,5-pentanediamine adipate dihydrate increased with the rising of temperature in all the selected binary solvent systems. For water + N,N-dimethylformamide, solubility increased as the mole fraction of water increased. However, the rising tendency changed when the temperature was higher than 303.15 K for water + methanol, and it would show a cosolvency phenomenon for water + ethanol. Furthermore, the solubility data were fitted with modified an Apelblat equation, NRTL model, combined nearly ideal binary solvent/Redlich Kister (CNIBS/R-K) model and Jouban–Acree model. The calculation results agreed well with the experimental data. Finally, the mixing thermodynamic properties of 1,5-pentanediamine adipate dihydrate in all tested solvents were calculated based on the experimental data and NRTL model. Full article
(This article belongs to the Special Issue Polymorphism in Crystals)
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10 pages, 4656 KiB  
Article
Crystal Structure Determination and Hirshfeld Analysis of a New Alternariol Packing Polymorph
by Kelly L. Rue, Guodong Niu, Jun Li and Raphael G. Raptis
Crystals 2022, 12(5), 579; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12050579 - 21 Apr 2022
Viewed by 2868
Abstract
A new polymorph of the mycotoxin alternariol is reported and characterized by single crystal X-ray diffraction. Structural data, Hirshfeld surface analysis, and 2D fingerprint plots are used to compare differences in the intermolecular interactions of the orthorhombic Pca21 Form I (previously [...] Read more.
A new polymorph of the mycotoxin alternariol is reported and characterized by single crystal X-ray diffraction. Structural data, Hirshfeld surface analysis, and 2D fingerprint plots are used to compare differences in the intermolecular interactions of the orthorhombic Pca21 Form I (previously reported) and the monoclinic P21/c Form II (herein reported). The polymorphs have small differences in planarity—7.55° and 2.19° between the terminal rings for Form I and Form II, respectively—that brings about significant differences in the crystal packing and O-H…H interactions. Full article
(This article belongs to the Special Issue Polymorphism in Crystals)
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13 pages, 4761 KiB  
Article
Baloxavir Marboxil Polymorphs: Investigating the Influence of Molecule Packing on the Dissolution Behavior
by Xinbo Zhou, Kaxi Yu, Jiyong Liu, Zhiping Jin and Xiurong Hu
Crystals 2022, 12(4), 550; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12040550 - 15 Apr 2022
Cited by 20 | Viewed by 2224
Abstract
Baloxavir marboxil (BXM) is a new blockbuster FDA-approved anti-influenza virus agent. However, its poor solubility has limited its oral bioavailability. In this study, BXM was crystallized from several organic solvents, obtaining three polymorphs, and their dissolution behaviors were studied. Detailed crystallographic examination revealed [...] Read more.
Baloxavir marboxil (BXM) is a new blockbuster FDA-approved anti-influenza virus agent. However, its poor solubility has limited its oral bioavailability. In this study, BXM was crystallized from several organic solvents, obtaining three polymorphs, and their dissolution behaviors were studied. Detailed crystallographic examination revealed that Form I is monoclinic, space group P21, with unit cell parameters a = 7.1159 (3) Å, b = 20.1967 (8) Å, c = 9.4878 (4) Å, β = 109.033 (1)°, V = 1289.02 (9) Å3, and Z = 2, and Form II is monoclinic, space group P21, with unit cell parameters a = 7.1002 (14) Å, b = 39.310 (7) Å, c = 9.7808 (18) Å, β = 110.966 (5)°, V = 2549.2 (8) Å3, and Z = 4. Form I has a rectangular three-dimensional energy frameworks net, while Form II has a two-dimensional net. On the other hand, Form II has a much larger percentage of its surface area of exposed hydrogen bond acceptors than Form I. These crystallographic features offered increased solubility and dissolution rate to Form II. The results of stability and solubility experiments suggest that Form II may be preferred in the solid form used for the industrial preparation of BXM medicinal products. Full article
(This article belongs to the Special Issue Polymorphism in Crystals)
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12 pages, 1526 KiB  
Article
Enhancement of Crystallization Process of the Organic Pharmaceutical Molecules through High Pressure
by Yaoguang Feng, Hongxun Hao, Yiqing Chen, Na Wang, Ting Wang and Xin Huang
Crystals 2022, 12(3), 432; https://doi.org/10.3390/cryst12030432 - 20 Mar 2022
Cited by 6 | Viewed by 1858
Abstract
The enhancement of the crystallization process through high pressures was studied by using ribavirin (RVB) as a model compound. The effects of high pressure on crystallization thermodynamics, nucleation kinetics, and process yield were evaluated and discussed. The solubility of ribavirin in three pure [...] Read more.
The enhancement of the crystallization process through high pressures was studied by using ribavirin (RVB) as a model compound. The effects of high pressure on crystallization thermodynamics, nucleation kinetics, and process yield were evaluated and discussed. The solubility of ribavirin in three pure solvents was measured at different pressures from 283.15 to 323.15 K. The results indicate that the solubility data of ribavirin decreased slightly when pressure was increased. The induction time of the cooling crystallization of ribavirin under different pressures was measured. The results show that high pressure could significantly reduce the nucleation induction period. Furthermore, the nucleation kinetic parameters under different pressures were calculated according to the classical nucleation theory. The effect of high pressure on the anti-solvent crystallization of ribavirin was also studied. Full article
(This article belongs to the Special Issue Polymorphism in Crystals)
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Review

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22 pages, 7997 KiB  
Review
Polytypes of sp2-Bonded Boron Nitride
by Bernard Gil, Wilfried Desrat, Adrien Rousseau, Christine Elias, Pierre Valvin, Matthieu Moret, Jiahan Li, Eli Janzen, James Howard Edgar and Guillaume Cassabois
Crystals 2022, 12(6), 782; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12060782 - 28 May 2022
Cited by 11 | Viewed by 3416
Abstract
The sp2-bonded layered compound boron nitride (BN) exists in more than a handful of different polytypes (i.e., different layer stacking sequences) with similar formation energies, which makes obtaining a pure monotype of single crystals extremely tricky. The co-existence of polytypes in [...] Read more.
The sp2-bonded layered compound boron nitride (BN) exists in more than a handful of different polytypes (i.e., different layer stacking sequences) with similar formation energies, which makes obtaining a pure monotype of single crystals extremely tricky. The co-existence of polytypes in a similar crystal leads to the formation of many interfaces and structural defects having a deleterious influence on the internal quantum efficiency of the light emission and on charge carrier mobility. However, despite this, lasing operation was reported at 215 nm, which has shifted interest in sp2-bonded BN from basic science laboratories to optoelectronic and electrical device applications. Here, we describe some of the known physical properties of a variety of BN polytypes and their performances for deep ultraviolet emission in the specific case of second harmonic generation of light. Full article
(This article belongs to the Special Issue Polymorphism in Crystals)
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15 pages, 4124 KiB  
Review
High-Pressure Polymorphism in Hydrogen-Bonded Crystals: A Concise Review
by Tingting Yan, Dongyang Xi, Qiuxue Fang, Ye Zhang, Junhai Wang and Xiaodan Wang
Crystals 2022, 12(5), 739; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12050739 - 20 May 2022
Cited by 3 | Viewed by 2445
Abstract
High-pressure polymorphism is a developing interdisciplinary field. Pressure up to 20 GPa is a powerful thermodynamic parameter for the study and fabrication of hydrogen-bonded polymorphic systems. This review describes how pressure can be used to explore polymorphism and surveys the reports on examples [...] Read more.
High-pressure polymorphism is a developing interdisciplinary field. Pressure up to 20 GPa is a powerful thermodynamic parameter for the study and fabrication of hydrogen-bonded polymorphic systems. This review describes how pressure can be used to explore polymorphism and surveys the reports on examples of compounds that our group has studied at high pressures. Such studies have provided insight into the nature of structure–property relationships, which will enable crystal engineering to design crystals with desired architectures through hydrogen-bonded networks. Experimental methods are also briefly surveyed, along with two methods that have proven to be very helpful in the analysis of high-pressure polymorphs, namely, the ab initio pseudopotential plane–wave density functional method and using Hirshfeld surfaces to construct a graphical overview of intermolecular interactions. Full article
(This article belongs to the Special Issue Polymorphism in Crystals)
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