scholarly journals Explainable machine learning for materials discovery: predicting the potentially formable Nd–Fe–B crystal structures and extracting the structure–stability relationship

IUCrJ ◽  
2020 ◽  
Vol 7 (6) ◽  
pp. 1036-1047
Author(s):  
Tien-Lam Pham ◽  
Duong-Nguyen Nguyen ◽  
Minh-Quyet Ha ◽  
Hiori Kino ◽  
Takashi Miyake ◽  
...  

New Nd–Fe–B crystal structures can be formed via the elemental substitution of LA–T–X host structures, including lanthanides (LA), transition metals (T) and light elements, X = B, C, N and O. The 5967 samples of ternary LA–T–X materials that are collected are then used as the host structures. For each host crystal structure, a substituted crystal structure is created by substituting all lanthanide sites with Nd, all transition metal sites with Fe and all light-element sites with B. High-throughput first-principles calculations are applied to evaluate the phase stability of the newly created crystal structures, and 20 of them are found to be potentially formable. A data-driven approach based on supervised and unsupervised learning techniques is applied to estimate the stability and analyze the structure–stability relationship of the newly created Nd–Fe–B crystal structures. For predicting the stability for the newly created Nd–Fe–B structures, three supervised learning models: kernel ridge regression, logistic classification and decision tree model, are learned from the LA–T–X host crystal structures; the models achieved maximum accuracy and recall scores of 70.4 and 68.7%, respectively. On the other hand, our proposed unsupervised learning model based on the integration of descriptor-relevance analysis and a Gaussian mixture model achieved an accuracy and recall score of 72.9 and 82.1%, respectively, which are significantly better than those of the supervised models. While capturing and interpreting the structure–stability relationship of the Nd–Fe–B crystal structures, the unsupervised learning model indicates that the average atomic coordination number and coordination number of the Fe sites are the most important factors in determining the phase stability of the new substituted Nd–Fe–B crystal structures.

Molecules ◽  
2021 ◽  
Vol 26 (23) ◽  
pp. 7178
Author(s):  
Yanqiang Han ◽  
Hongyuan Luo ◽  
Qianqian Lu ◽  
Zeying Liu ◽  
Jinyun Liu ◽  
...  

The long-acting parenteral formulation of the HIV integrase inhibitor cabotegravir (GSK744) is currently being developed to prevent HIV infections, benefiting from infrequent dosing and high efficacy. The crystal structure can affect the bioavailability and efficacy of cabotegravir. However, the stability determination of crystal structures of GSK744 have remained a challenge. Here, we introduced an ab initio protocol to determine the stability of the crystal structures of pharmaceutical molecules, which were obtained from crystal structure prediction process starting from the molecular diagram. Using GSK744 as a case study, the ab initio predicted that Gibbs free energy provides reliable further refinement of the predicted crystal structures and presents its capability for becoming a crystal stability determination approach in the future. The proposed work can assist in the comprehensive screening of pharmaceutical design and can provide structural predictions and stability evaluation for pharmaceutical crystals.


2013 ◽  
Vol 68 (5-6) ◽  
pp. 616-624 ◽  
Author(s):  
Tanja Schustereit ◽  
Harald Henning ◽  
Thomas Schleid ◽  
Ingo Hartenbach

The lanthanoid(III) bromide ortho-oxomolybdates(VI) LnBr[MoO4] (Ln = Pr, Nd, Sm, Gd - Lu) crystallize triclinically in the space group P1 (a=686 - 689, b=713 - 741, c=1066 - 1121 pm, a =103 - 106, b =107 - 108, g = 92 - 95°) with Z =4. The crystal structure contains two crystallographically distinguishable Ln3+ cations, each one with a coordination number of seven plus one. (Ln1)3+ is surrounded by three bromide and four plus one oxide anions, while for (Ln2)3+ just one bromide and six plus one oxide anions belong to the coordination sphere. Considering the smallest lanthanoids, however, the distances to the farthest anions increase so much that their contribution to the coordination spheres becomes negligible in both cases. The polyhedra around (Ln1)3+ are connected to each other via common edges, which consist of two crystallographically identical Br- anions (Br1). Furthermore, the common structure of the LnBr[MoO4] series contains two crystallographically different, discrete [MoO4]2- ortho-oxomolybdate(VI) tetrahedra. Two plus one oxygen atoms of each [(Mo1)O4]2- unit are used to interconnect the polyhedra around (Ln1)3+ and (Ln2)3+ together with one Br- anion (Br2). The connection between two polyhedra around (Ln2)3+ is generated exclusively by two plus one oxygen atoms of two [(Mo2)O4]2- anions. The complete structural arrangement can be considered as a bundle of primitively packed 1¥{LnBr[MoO4]} chains with two alternating motifs of linkage, which are running parallel along [012].


1984 ◽  
Vol 39 ◽  
Author(s):  
Yoshinao Mishima ◽  
Yoshihiro Oya ◽  
Tomoo Suzuki

ABSTRACTThe present paper deals with the occurence and magnitude of characteristic mechanical anomalies observed in many L12 intermetallic compounds and their relation to the phase stability of the crystal structure against other geometrically closed packed(GCP) phases. The dislocation configurations in the crystal structure and resultant plastic behavior are in close relation with anti-phase boundary(APB) and stacking fault(SF) energies in the compounds, while the relative magnitude of these energies on various crystallographic planes actually determines the phase stability of the L12 crystal structure. It is shown here, based on our series of investigations carried out over the past decade, that the general tendencies for particular deformation modes to occur can be systematically interpreted in terms of alloy chemistry of the compounds, including variables such as combination of component species, nonstoichiometry and ternary additions in the compounds, all of which affect the stability of the phase.


Author(s):  
Michael Ketter ◽  
Matthias Weil

Single crystals of Cs2SnSi6O15, dicaesium tin(IV) hexasilicate, were serendipitously obtained from a CsCl/NaCl flux at 923 K, starting from mixtures of CaO, SnO and TeO2 in a closed silica ampoule. The crystal structure of Cs2SnSi6O15 is constructed from {Si6O15}6– layers extending parallel to (101), and CsI cations with a coordination number of eleven as well as isolated [SnO6] octahedra situated between the silicate layers. Each of the nine different SiO4 tetrahedra in the silicate layer has a connectedness of Q 3 (three bridging and one terminal O atom), which leads to the formation of five- and eight-membered rings. The same type of silicate layer is found in the crystal structure of the mineral zeravshanite. Comparison with other silicates of the type Cs2 M IVSi6O15 (M IV = Ti, Zr, Th, U) revealed a klassengleiche group–subgroup relationship of index 2 between Cs2ZrSi6O15 (Z = 6, space group C2/m) and Cs2SnSi6O15 (Z = 12, space group I2/c).


1977 ◽  
Vol 30 (12) ◽  
pp. 2647 ◽  
Author(s):  
D Taylor

Crystals of tetrakis(4-benzylpyridine)dimercury(I) perchlorate, [Hg2(C12H11N)4]2, (ClO4)2, are monoclinic,a 11.729(1) Ǻ, b 10.896(1) Ǻ, c 18.392(2) Ǻ, β 96.20(1)�, space group P21/c with Z = 2 dimeric formula units. The structure was solved from three-dimensional diffractometer data (2744 independent reflections) by Patterson and Fourier techniques. Block-diagonal least-squares refinement of all non-hydrogen atoms converged at R 0.039, Rw 0.053. The mercury atoms in the centrosymmetric cation are three-coordinate with Hg-Hg 2.5084(7), Hg-N 2.227(7), 2.476(7) Ǻ. The Hg-Hg-N angles are 153.9� and 118.4� respectively. The perchlorate ions span the Hg-Hg bond with long Hg-O contacts of 2.899 and 3.026 Ǻ. This is a new structural type for dimercury(1) coordination compounds. The distortion of the usually linear L-Hg-Hg-L system with the increase in coordination number of the mercury atoms appears to be related to the stability of dimercury(I) complexes with moderately basic N-donor ligands.


Chemistry ◽  
2021 ◽  
Vol 3 (1) ◽  
pp. 45-73
Author(s):  
Matthias Weil

During a systematic study of monofluorophosphates, i.e., compounds comprising the tetrahedral anion PO3F2−, twelve, for the most part new, compounds were obtained from aqueous solutions. Crystal structure refinements based on single crystal X-ray diffraction data revealed the previously unknown crystal structures of CdPO3F(H2O)2, Cr2(PO3F)3(H2O)18.8, Pb2(PO3F)Cl2(H2O), (NH4)2M(PO3F)2(H2O)2 (M = Mg, Mn, Co), NH4Cr(PO3F)2(H2O)6, NH4Cu2(H3O2)(PO3F)2, (NH4)2Zn(PO3F)2(H2O)0.2, and (NH4)2Zn3(PO3F)4(H2O), as well as redeterminations of ZnPO3F(H2O)2.5 and (NH4)2Ni(PO3F)2(H2O)6. From the previously unknown crystal structures, CdPO3F(H2O)2 (space group P-1), Cr2(PO3F)3(H2O)18.8 (P-1), Pb2(PO3F)Cl2(H2O) (Pnma), NH4Cr(PO3F)2(H2O)6 (R-3m), (NH4)2Zn(PO3F)2(H2O)0.2 (C2/c), and (NH4)2Zn3(PO3F)4(H2O) (I-43d) each crystallizes in an unique crystal structure, whereas compounds (NH4)2M(PO3F)2(H2O)2 (M = Mg, Co) crystallize in the (NH4)2Cu(PO3F)2(H2O)2 type of structure (C2/m) and (NH4)2Mn(PO3F)2(H2O)2 in a subgroup thereof (P21/n, with a klassengleiche relationship of index 2), and NH4Cu2(H3O2)(PO3F)2 (C2/m) crystallizes isotypically with natrochalcite-type KCu2(H3O2)(SO4)2. A survey on the PO3F2− anion, including database entries of all inorganic compounds comprising this group, revealed mean bond lengths of P–O = 1.506(13) Å, P–F = 1.578(20) Å, and angles of O–P–O = 113.7(1.7)° and O–P–F = 104.8(1.7)°, using a dataset of 88 independent PO3F2− anions or entities. For those crystal structures of monofluorophosphates where hydrogen bonding is present, in the vast majority of cases, hydrogen bonds of the type D–H···F–P (D = O, N) are not developed.


1977 ◽  
Vol 30 (10) ◽  
pp. 2153 ◽  
Author(s):  
CL Raston ◽  
D Wege ◽  
AH White

The crystal structure of the title compound, [Fe(CO)4(C10H8O)], has been determined at 295 K from diffractometer data, and refined by least squares to a residual of 0.073 for 2990 ?observed? reflections. Crystals are triclinic, Pī, a 22.980(6), b 9.385(3), c 6.313(2) Ǻ, α 85.22(3), β 87.67(3), γ 79.48(3)�, Z4. The two independent molecules in the same cell differ only trivially in their geometries, the coordination number about the metal being essentially five: four carbonyls and the ethylene double bond in a pseudo-trigonal-bipyramidal arrangement. From distortions observed within the molecular geometry as a result of steric interactions between the epoxide oxygen and the nearby axial carbonyl, it clearly emerges that the stability of the present derivative relative to that of methylene bridged ligands is simply a consequence of the greatly increased stereochemical interaction of the latter and not of any electronic effect.


1987 ◽  
Vol 2 (1) ◽  
pp. 16-27 ◽  
Author(s):  
Raghavan Ayer ◽  
J. C. Scanlon ◽  
T. A. Ramanarayanan ◽  
R. R. Mueller ◽  
R. Petkovic-Luton ◽  
...  

The crystal structure and chemical composition of the intermetallic phase in a Fe-20%Cr-4%Al-0.5%Y (wt. %) alloy were investigated by electron microscopy. Convergent beam diffraction studies revealed that the intermetallic phase forms in three different crystal structures that could coexist in a single grain of the phase. The dominant crystal structure was shown to be hexagonal (a = 0.85, c = 0.84 nm) with a space group most likely to be P63/mmc. Within the hexagonal phase, regions of a rhombohedral crystal structure (a = 0.85, c = 1.26 nm) were observed that had grown in without an apparent phase boundary separating the two crystal structures. The third crystal structure was determined to be monoclinic (a = 0.97, b = 0.85, c = 1.07 nm, and beta = 97.3°) and formed by twinning on the {10$\overline 1$1} planes of the hexagonal phase. The chemical compositions of regions with different crystal structures were comparable and the stoichiometry of the intermetallic phase corresponds to (Fe,Cr)17 (Al,Y)2. The relationship of the observed crystal structures to those previously reported is discussed.


2004 ◽  
Vol 848 ◽  
Author(s):  
E. A. Juarez-Arellano ◽  
J. Campa-Molina ◽  
S. Ulloa-Godínez ◽  
L. Bucio ◽  
E. Orozco

ABSTRACTIn this article we present the main features and structural relationships between thortveitite-type and thortveitite-like germanates compounds. We describe in detail the crystal structures, how they are built and the difference between them. Bond-valence and polyhedra distortion analysis are made and crystal structure stability ranges are given.


2020 ◽  
Vol 8 (44) ◽  
pp. 15852-15859
Author(s):  
Jiu Chen ◽  
Fuhua Li ◽  
Yurong Tang ◽  
Qing Tang

Chemical functionalization can significantly improve the stability of meta-stable 1T′-MoS2 and tune the surface HER activity.


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