scholarly journals Powder diffraction and crystal structure prediction identify four new coumarin polymorphs

2017 ◽  
Vol 8 (7) ◽  
pp. 4926-4940 ◽  
Author(s):  
Alexander G. Shtukenberg ◽  
Qiang Zhu ◽  
Damien J. Carter ◽  
Leslie Vogt ◽  
Johannes Hoja ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Powder Diffraction ◽  
Structure Prediction ◽  
Prediction Method ◽  
Crystal Structure Prediction ◽  
Free Energies ◽  
Structure Prediction Method

Crystal structures of four new coumarin polymorphs were solved by crystal structure prediction method and their lattice and free energies were calculated by advanced techniques.

Electronic structure and photocatalytic band offset of few-layer GeP2

2017 ◽  
Vol 5 (42) ◽  
pp. 22146-22155 ◽  
Author(s):  
Fazel Shojaei ◽  
Jae Ryang Hahn ◽  
Hong Seok Kang
Keyword(s):  
Crystal Structure ◽  
Electronic Structure ◽  
Structure Prediction ◽  
Prediction Method ◽  
Group Iv ◽  
Band Offset ◽  
Two Dimensional ◽  
Crystal Structure Prediction ◽  
T Phase ◽  
Structure Prediction Method

Based on a sophisticated crystal structure prediction method, we propose two-dimensional (2D) GeP2in the tetragonal (T) phase never observed for other group IV–V compounds.

scholarly journals Crystal structures of two furazidin polymorphs revealed by a joint effort of crystal structure prediction and NMR crystallography

2020 ◽  
Vol 76 (3) ◽  
pp. 322-335 ◽  
Author(s):  
Marta K. Dudek ◽  
Piotr Paluch ◽  
Edyta Pindelska
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Structure Determination ◽  
Structure Prediction ◽  
Structural Features ◽  
Crystal Structure Determination ◽  
Crystal Structure Prediction ◽  
Crystal Forms ◽  
Space Groups ◽  
Nmr Crystallography

This work presents the crystal structure determination of two elusive polymorphs of furazidin, an antibacterial agent, employing a combination of crystal structure prediction (CSP) calculations and an NMR crystallography approach. Two previously uncharacterized neat crystal forms, one of which has two symmetry-independent molecules (form I), whereas the other one is a Z′ = 1 polymorph (form II), crystallize in P21/c and P 1 space groups, respectively, and both are built by different conformers, displaying different intermolecular interactions. It is demonstrated that the usage of either CSP or NMR crystallography alone is insufficient to successfully elucidate the above-mentioned crystal structures, especially in the case of the Z′ = 2 polymorph. In addition, cases of serendipitous agreement in terms of 1H or 13C NMR data obtained for the CSP-generated crystal structures different from the ones observed in the laboratory (false-positive matches) are analyzed and described. While for the majority of analyzed crystal structures the obtained agreement with the NMR experiment is indicative of some structural features in common with the experimental structure, the mentioned serendipity observed in exceptional cases points to the necessity of caution when using an NMR crystallography approach in crystal structure determination.

scholarly journals ROY revisited, again: the eighth solved structure

2018 ◽  
Vol 211 ◽  
pp. 477-491 ◽  
Author(s):  
Melissa Tan ◽  
Alexander G. Shtukenberg ◽  
Shengcai Zhu ◽  
Wenqian Xu ◽  
Eric Dooryhee ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Structure Prediction ◽  
Crystal Structure Prediction ◽  
X Ray ◽  
Prediction Algorithms

X-ray powder diffraction and crystal structure prediction algorithms are used in synergy to establish the crystal structure of the eighth polymorph of ROY, form R05.

scholarly journals Theoretical Prediction of Crystal Polymorphs for Organic Molecules

2014 ◽  
Vol 70 (a1) ◽  
pp. C1626-C1626
Author(s):  
Shigeaki Obata ◽  
Mitsuaki Sato ◽  
Hitoshi Goto
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Structure Prediction ◽  
High Speed ◽  
Prediction Method ◽  
Energy Calculation ◽  
Crystal Polymorphism ◽  
Energy Evaluation ◽  
Target Molecules ◽  
Experimental Crystal

Crystal structure prediction is one of the useful theoretical tools for designing and synthesizing new materials in pharmaceutical therapeutics and industrial electronics. Furthermore, the prediction can provide immense valuable scientific knowledge on a crystal growth, polymorphism and many properties of organic molecular crystals. Therefore, we have started the development of high-speed and high-accurate prediction method for organic molecular crystal structures [1,2]. In this work, we demonstrate the theoretical predictions of crystal structures of fourteen target molecules that were used in the international competitions known as CSP blind tests hosted by CCDC [3]. All strategies required for crystal lattice construction expanded to a given effective crystal radius, crystal energy calculation with the reliable molecular force field (MMFF94s) and exhaustive geometry search included a variety of crystal polymorphism are implemented into CONFLEX program [1]. As the results of the applications, we confirmed in all cases of target molecules that, at least, one calculated crystal structure in agreement with the corresponding observed ones can be found. Essential ability required for the prediction method to survive the CSP competitions is that the experimental crystal structure can computationally reproduce within top 3 of most stable structures in crystal energy evaluation. In these tests, only three applications to the target I (Orth. polymorph), II and VIII can successfully satisfy the demand. Details will be discussed in this conference.

scholarly journals Crystal structure prediction of organic pigments: quinacridone as an example

2007 ◽  
Vol 40 (1) ◽  
pp. 105-114 ◽  
Author(s):  
N. Panina ◽  
F. J. J. Leusen ◽  
F. F. B. J. Janssen ◽  
P. Verwer ◽  
H. Meekes ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Energy Minimization ◽  
Structure Prediction ◽  
Crystal Structure Prediction ◽  
X Ray ◽  
Organic Pigments ◽  
Structural Database ◽  
Diffraction Patterns ◽  
Experimental Structure

The structures of the α, β and γ polymorphs of quinacridone (Pigment Violet 19) were predicted usingPolymorph Predictorsoftware in combination with X-ray powder diffraction patterns of limited quality. After generation and energy minimization of the possible structures, their powder patterns were compared with the experimental ones. On this basis, candidate structures for the polymorphs were chosen from the list of all structures. Rietveld refinement was used to validate the choice of structures. The predicted structure of the γ polymorph is in accordance with the experimental structure published previously. Three possible structures for the β polymorph are proposed on the basis of X-ray powder patterns comparison. It is shown that the α structure in the Cambridge Structural Database is likely to be in error, and a new α structure is proposed. The present work demonstrates a method to obtain crystal structures of industrially important pigments when only a low-quality X-ray powder diffraction pattern is available.

scholarly journals Nicotinamide: Seven New Polymorphic Structures Revealed by Melt Crystallization and Crystal Structure Prediction

2020 ◽  
Author(s):  
Xizhen Li ◽  
Xiao Ou ◽  
Bingquan Wang ◽  
Haowei Rong ◽  
Bing Wang ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Crystal Structures ◽  
Structure Prediction ◽  
Crystal Structure Prediction ◽  
Melt Crystallization ◽  
Efficient Tool ◽  
Single Crystal Structures ◽  
Solution Crystallization

<p>Here, we reported nicotinamide (NIC), a long-known vitamin, was revealed in fact to be a highly polymorphic compound with nine solved single-crystal structures by performing melt crystallization. A CSP calculation successfully identified all six Z’ = 1 and 2 experimental structures. Melt crystallization has turned out to be an efficient tool for exploring polymorphic landscape, especially in regions inaccessbile by solution crystallization.</p>

scholarly journals Crystal Structure Prediction and Lattice Dynamical Calculations for the Rare Platinum-Group Mineral Zaccariniite (RhNiAs)

Minerals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 98
Author(s):  
Jordi Ibáñez-Insa
Keyword(s):  
Crystal Structure ◽  
Structure Prediction ◽  
Density Functional ◽  
Prediction Method ◽  
Theoretical Data ◽  
Crystal Structure Prediction ◽  
Mineral Density ◽  
Starting Point ◽  
Platinum Group ◽  
Structural Methods

The crystal structures of newly found minerals are routinely determined using single-crystal techniques. However, many rare minerals usually form micrometer-sized aggregates that are difficult to study with conventional structural methods. This is the case for numerous platinum-group minerals (PGMs) such as, for instance, zaccariniite (RhNiAs), the crystal structure of which was first obtained by studying synthetic samples. The aim of the present work is to explore the usefulness of USPEX, a powerful crystal structure prediction method, as an alternative means of determining the crystal structure of minerals such as zaccariniite, with a relatively simple crystal structure and chemical formula. We show that fixed composition USPEX searches with a variable number of formula units, using the ideal formula of the mineral as the only starting point, successfully predict the tetragonal structure of a mineral. Density functional theory (DFT) calculations can then be performed in order to more tightly relax the structure of the mineral and calculate different fundamental properties, such as the frequency of zone-center Raman-active phonons, or even their pressure behavior. These theoretical data can be subsequently compared to experimental results, which, in the case of newly found minerals, would allow one to confirm the correctness of the crystal structure predicted by the USPEX code.

Sign in / Sign up

Export Citation Format

Share Document