Microscopic origin of pressure-induced phase-transitions in urea: a detailed investigation through first principles calculations

Abraham, B. M.; Adivaiah, B.; Vaitheeswaran, G.

doi:10.1039/c8cp04827d

Cited by 17 publications

(10 citation statements)

References 78 publications

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“…Following Gibbs energy contributions can lead to a new understanding of reasons for phase transitions for any crystalline material. In some cases, it is possible to claim volume change (PV), energy (E inter or E intra ), enthalpy (H) or entropy (S) as a driving force for phase transition [61,67,81,89] DFT methods can be applied to experimental structures, obtained at some pressure, and all the above-mentioned parameters can be calculated. If one needs thermodynamic parameters for crystal structure at a pressure where no experimental data available, there are two main possibilities.…”

Section: Dft Methodsmentioning

confidence: 99%

A Short Review of Current Computational Concepts for High-Pressure Phase Transition Studies in Molecular Crystals

Rychkov

2020

Crystals

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High-pressure chemistry of organic compounds is a hot topic of modern chemistry. In this work, basic computational concepts for high-pressure phase transition studies in molecular crystals are described, showing their advantages and disadvantages. The interconnection of experimental and computational methods is highlighted, showing the importance of energy calculations in this field. Based on our deep understanding of methods’ limitations, we suggested the most convenient scheme for the computational study of high-pressure crystal structure changes. Finally, challenges and possible ways for progress in high-pressure phase transitions research of organic compounds are briefly discussed.

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Section: Dft Methodsmentioning

confidence: 99%

A Short Review of Current Computational Concepts for High-Pressure Phase Transition Studies in Molecular Crystals

Rychkov

2020

Crystals

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“…The hydrogen bonds in crystalline urea undergo a considerable strengthening upon compression, which was confirmed by the softening of the vibrational modes involving the N-H groups [20]. A very detailed knowledge of urea polymorphic structures enables to compare the experimental and computational results [21] and gives the chance to accurately optimize the calculation methodology that would also be suitable for other organic polymorphs. Therefore, using urea as a model compound, we have decided to conduct the computational study in order to explore the possible application of periodic DFT calculations in predicting the pressure induced polymorphic phase transition.…”

Section: Polymorphism Of Ureamentioning

confidence: 97%

Can We Predict the Pressure Induced Phase Transition of Urea? Application of Quantum Molecular Dynamics

2020

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Crystalline urea undergoes polymorphic phase transition induced by high pressure. Form I, which is the most stable form at normal conditions and Form IV, which is the most stable form at 3.10 GPa, not only crystallize in various crystal systems but also differ significantly in the unit cell dimensions. The aim of this study was to determine if it is possible to predict polymorphic phase transitions by optimizing Form I at high pressure and Form IV at low pressure. To achieve this aim, a large number of periodic density functional theory (DFT) calculations were performed using CASTEP. After geometry optimization of Form IV at 0 GPa Form I was obtained, performing energy minimization of Form I at high pressure did not result in Form IV. However, employing quantum molecular isothermal–isobaric (NPT) dynamics calculations enabled to accurately predict this high-pressure transformation. This study shows the potential of different approaches in predicting the polymorphic phase transition and points to the key factors that are necessary to achieve the success.

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“…However, after its apparent discovery by Birdgman in 1916, it has been never experimentally achieved. It was only in 2019 when the research proved the nonexistence of phase II and its coincidence with phase IV in room temperature [150]. Such an experimental approach has reopened the computational investigation of urea structure as only phase I, III, and IV own a detailed structure description [151].…”

Section: Pressure and Temperature Stability Dependencementioning

confidence: 99%

Periodic DFT Calculations—Review of Applications in the Pharmaceutical Sciences

2020

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In the introduction to this review the complex chemistry of solid-state pharmaceutical compounds is summarized. It is also explained why the density functional theory (DFT) periodic calculations became recently so popular in studying the solid APIs (active pharmaceutical ingredients). Further, the most popular programs enabling DFT periodic calculations are presented and compared. Subsequently, on the large number of examples, the applications of such calculations in pharmaceutical sciences are discussed. The mentioned topics include, among others, validation of the experimentally obtained crystal structures and crystal structure prediction, insight into crystallization and solvation processes, development of new polymorph synthesis ways, and formulation techniques as well as application of the periodic DFT calculations in the drug analysis.

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Microscopic origin of pressure-induced phase-transitions in urea: a detailed investigation through first principles calculations

Abstract: Pressure induced phase transitions of urea are identified. The violation of Born stability criteria in the P212121 structure along with acoustic mode softening in the U–R direction are responsible for P212121 → P21212.

Cited by 17 publications

References 78 publications

A Short Review of Current Computational Concepts for High-Pressure Phase Transition Studies in Molecular Crystals

A Short Review of Current Computational Concepts for High-Pressure Phase Transition Studies in Molecular Crystals

Can We Predict the Pressure Induced Phase Transition of Urea? Application of Quantum Molecular Dynamics

Periodic DFT Calculations—Review of Applications in the Pharmaceutical Sciences

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