Crystal structures

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Molecular packing groups and ab initio crystal-structure prediction. A 55 , — Williams, D. Mooij, W. Ab initio crystal structure predictions for flexible hydrogen-bonded molecules. Allen, F. Systematic analysis of structural data as a research technique in organic chemistry. Sarma, J. The supramolecular synthon approach to crystal structure prediction. Transferable ab initio intermolecular potentials. Validation and application to crystal structure prediction.

Leusen, F. Ab initio prediction of polymorphs. Growth , — Dong, Z. Crystal structure of neotame anhydrate polymorph G. Chin, D. Improving the efficiency of predicting hydrogen-bonded organic molecules. Prediction of molecular crystal structures by Monte Carlo simulated annealing without reference to diffraction data. Explains the application of the Monte Carlo method in predicting crystal structures. Hammond, R. Ulrich, J. Determining the crystal structures of organic solids using x-ray powder diffraction together with molecular and solid state modeling techniques.

Harris, K. Crystals structure determination from powder diffraction data. Explains the prediction of the crystal structure of compounds from their powder diffraction data only. Aakeroy, C. A combination of X-ray single crystal diffraction and Monte Carlo structure solution from X-ray powder diffraction data in a structural investigation of 5-bromonicotinic acid and solvates thereof. Will, G. POWLS: a powder least-squares program. Pawley, G. Unit-cell refinement from powder diffraction scans.

Langford, J. High-resolution powder diffraction studies of copper II oxide.


The breadth and shape of instrumental line profiles in high-resolution powder diffraction. Crystal-structure refinement by profile fitting and least-squares analysis of powder diffractometer data. Applications of total pattern fitting to a study of crystallite size and strain in zinc oxide powder. Powder Diffract. David, W. Routine determination of molecular crystal structures from powder diffraction data. Shankland, K. Crystal structure determination from powder diffraction data by the application of a genetic algorithm.

The genetic algorithm: foundations and applications in structure solution from powder diffraction data. A 54 , — Explains the use of the genetic algorithm for predicting the crystal structure of compounds from their powder diffraction pattern. Computationally assisted structure determination for molecular materials from X-ray powder diffraction data. Crystal structure determination from powder diffraction data by Monte Carlo methods. A genetic algorithm for crystal structure solution from powder diffraction data. Recent advances in opportunities for solving molecular crystal structures directly from powder diffraction data: new insights in crystal engineering contexts.

Turner, G. Implementation of Lamarckian concepts in a genetic algorithm for structure solution from powder diffraction data. Habershon, S. Gaining insights into the evolutionary behavior in genetic algorithm calculations, with applications in structure solution from powder diffraction data. Lanning, O. Definition of a 'guiding function' in global optimization: a hybrid approach combining energy and R-factor in structure solution from powder diffraction data.

Gilmore, C. Maximum entropy and Bayesian statistics in crystallography: a review of practical applications. A 52 , — Explains the use of the maximum entropy algorithm for the prediction of the crystal structures of compounds and reviews its application. Applications of the maximum entropy method to powder diffraction and electron crystallography. A , 97— Braga, D. Innovation in crystal engineering. Pepinsky, R. Crystal engineering-new concept in crystallography.

II , Schmidt, G. Photodimerization in solid state. Pure Appl. Panunto, T. Hydrogen-bond formation in nitroanilines: the first step in designing acentric materials. Comprehensive work summarizing the recent achievements and future trends in crystal engineering. Supramolecular synthons in crystal engineering — a new organic synthesis. Edn Eng. Walsh, B. Crystal engineering of the composition of pharmaceutical phases. Bis, J. McMahon, J. Fleischman, S. Remenar, J. Crystal engineering of novel cocrystals of a triazole drug with 1,4-dicarboxylic acids.

Payne, R. The mechanical properties of two forms of primidone predicted from their crystal structures. Roberts, R. Mechanical property predictions for polymorphs of sulphathiazole and carbamazepine. Brittle—ductile transitions in die compaction of sodium chloride. Determination of the critical stress intensity factor KIC of microcrystalline cellulose using radially edge-cracked tablets. Bassam, F. Young's modulus of powders used as pharmaceutical excipients. The relationship between Young's modulus of elasticity of organic solids and their molecular structure.

Powder Technol. Nangia, A.


Database research in crystal engineering. Ten years of experience in polymorph prediction: what next? Rohl, A. Computer prediction of crystal morphology. Rajeswaran, M. Three-dimensional structure determination of N- p-tolyl -dodecylsulfonamide from powder diffraction data and validation of structure using solid-state NMR spectroscopy. Tishmack, P. R Solid-state nuclear magnetic resonance spectroscopy — pharmaceutical applications. Reutzel-Edens, S. Solid-state NMR spectroscopy of small molecules: from NMR crystallography to the characterization of solid oral dosage forms.

Bugay, D. Characterization of the solid-state:spectroscopic techniques. Drug Del. Taylor, L. Evaluation of solid-state forms present in tablets by Raman spectroscopy. Kempf, D. ABT is a potent inhibitor of human immunodeficiency virus protease and has high oral bioavailability in humans. Natl Acad. USA 92 , — Chemburkar, S. Dealing with the impact of ritonavir polymorphs on the late stages of bulk drug process development. Young, A.

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Explains the Rietveld refinement method in detail. McCusker, L. Rietveld refinement guidelines. Potential applications of Rietveld analysis in the pharmaceutical industry. Kisi, E. Rietveld analysis of powder diffraction patterns. Forum 18 , — Rietveld, H. Profile refinement method for nuclear and magnetic structures. Download references. Correspondence to David J. Cambridge Crystallographic Data Centre. The transformation of a solid from one physical form to another.

Phase transformation can involve the transformation of a single component into one or more components, and can result from changes in physical conditions, as in pharmaceutical processing. Examples of phase transformation include polymorphic transitions, crystallization of amorphous solids, and solid-state solvation and desolvation.

A crystal is termed a molecular adduct when its lattice consists of more than one chemical component. A solid phase that contains solvent molecules, in addition to molecules of the major component, in the crystal lattice. A solid phase that contains water molecules, in addition to molecules of the major component, in the crystal lattice.

An attractive interaction between two electronegative atoms through a hydrogen bridge. The hydrogen bond is partly electrostatic and partly covalent in nature, with limited orbital overlap between the participating atoms. Of the two electronegative atoms, one is the proton donor and the other is a proton acceptor. When present within the same molecule, a hydrogen bond is termed intramolecular. When present between two molecules, a hydrogen bond is termed intermolecular. The term slip refers to the translational motion of lattice planes relative to each other. Such planes are termed slip planes.

A family of slip planes, together with the slip direction, is termed a slip system. The members of a pair of polymorphs are termed enantiotropes when their mutual transition temperature is less than the melting point of either polymorph. Each enantiotrope has its own temperature range of stability.

1. Crystal structures

The members of a pair of polymorphs are termed monotropes when they have no mutual transition temperature. One monotrope is always more stable than the other polymorph under all conditions in which the solid state can exist. In an isolated site hydrate, the water molecules in the crystal lattice of the hydrate are isolated from direct contact with other water molecules by intervening molecules of the major component.

In an ion-associated hydrate, the water molecules in the crystal lattice of the hydrate are coordinated to certain ions often metal ions. In a channel hydrate, the water molecules present in the crystal lattice of the hydrate lie next to other water molecules of adjoining unit cells, forming channels through the crystals along a direction in the lattice. An expanded channel hydrate can take up water into the channels when exposed to relatively high humidity and can release water from the channels when exposed to relatively low humidity.

The crystal lattice can expand or contract as hydration or dehydration proceeds, changing the dimensions of the unit cell. A planar hydrate is a channel hydrate in which water molecules are localized in a plane, corresponding to two-dimensional order. A solid solution can be substitutional or interstitial. A substitutional solid solution is a homogeneous crystalline phase in which some of the constituent molecules are substituted by foreign molecules that possess sufficient similarity that the lattice dimensions are changed only slightly.

In an interstitial solid solution, the foreign molecules are inserted into interstitial positions, such that the lattice dimensions are changed only slightly. An electron accelerator that uses synchronized magnetic fields. When the high-speed electrons are directed to collide with an appropriate target, high-energy X-ray radiation or ultraviolet radiation is produced. When a solid is heated beyond its melting temperature, it fuses melts to produce a liquid that can be termed a melt.

The growth of one crystal on the surface of another crystal the substrate , on which the growth of the deposited crystal is oriented by the lattice structure of the substrate. A specific crystallization technique in which the crystals nucleate and grow inside a capillary as a result of slow solvent evaporation.

The systematic absence of specific groups of reflections in a diffraction pattern of a crystal indicates the presence of certain symmetry elements and enables the crystallographic space group of the crystal lattice to be defined. In the isomorphous replacement method, a heavy atom is introduced into the crystal lattice without disrupting the original crystal structure. The new crystal obtained is known as the derivative crystal. The aim of isomorphous replacement is to obtain the structure of the original crystal by constructing a map that is, a Patterson map of the difference in electron density between the diffraction pattern of the derivative crystal and that of the heavy atom.

This method is used to determine the crystal structures of proteins. An amorphous capsule that is used to achieve the required oral bioavailability of extremely water-insoluble drugs, such as itraconazole. A measure of a material's elasticity, which is defined as the force per unit cross-section of the material divided by the fractional increase in length that results from the stretching of a standard specimen of the material. Reprints and Permissions. The Journal of Chemical Thermodynamics Nature Materials Crystals Advanced search.

Skip to main content. Abstract Most marketed pharmaceuticals consist of molecular crystals. Key Points The crystalline form of a drug affects properties such as its solubility, stability, dissolution rate, bioavailability and tabletability, and so understanding the crystalline state is crucial for many of the activities of the pharmaceutical industry. The lattices in two dimensions are the square lattice, the rectangular lattice, the centered rectangular lattice, the hexagonal lattice and the oblique lattice as shown in Figure 2.

It is customary to organize these lattices in groups, which have the same symmetry. An example is the rectangular and the centered rectangular lattice. As can be seen on the figure, all the lattice points of the rectangular lattice can be obtained by a combination of the lattice vectors. The centered rectangular lattice can be constructed in two ways.

It can be obtained by starting with the same lattice vectors as those of the rectangular lattice and then adding an additional atom at the center of each rectangle in the lattice. This approach is illustrated by Figure 2. The lattice vectors generate the traditional unit cell and the center atom is obtained by attaching two lattice points to every lattice point of the traditional unit cell.

The alternate approach is to define a new set of lattice vectors, one identical to and another starting from the same origin and ending on the center atom. These lattice vectors generate the so-called primitive cell and directly define the centered rectangular lattice. These five lattices are summarized in Table 2. The same approach is used for lattices in three dimensions. The fourteen lattices of three-dimensional crystals are classified as shown in Table 2. The cubic lattices are an important subset of these fourteen Bravais lattices since a large number of semiconductors are cubic.

The three cubic Bravais lattices are the simple cubic lattice, the body-centered cubic lattice and the face-centered cubic lattice as shown in Figure 2.

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  7. Since all unit vectors identifying the traditional unit cell have the same size, the crystal structure is completely defined by a single number. This number is the lattice constant, a. Crystal planes of a crystal are characterized by their Miller indices. The Miller indices are defined as the smallest possible integers, which have the same ratios as the inverse of the intersections of a given plane with a set of axis defined by the unit vectors of that crystal.

    Crystal Structure Review

    This definition is further illustrated with Figure 2. The intersections between the plane and the axis occur at p, q, and r. The corresponding Miller indices are therefore , where A is an integer chosen such that the Miller indices are the smallest possible integers. It should be noted that the resulting Miller indices are the same for all parallel planes of atoms in a crystal. Find the smallest integers proportional to the inverse of the intercepts. These are obtained in this case by multiplying each fraction by The Miller indices of this plane and all parallel planes are therefore.

    Crystal structure

    Note that the negative indices are indicated with a bar above the integer for a more compact notation. Each atom in the diamond lattice has a covalent bond with four adjacent atoms, which together form a tetrahedron. This lattice can also be formed from two face-centered-cubic lattices, which are displaced along the body diagonal of the larger cube in Figure 2. The diamond lattice therefore is a face-centered-cubic lattice with a basis containing two identical atoms. CdaA is the sole di-adenylate cyclase in L. Here we report crystal structures of CdaA from L.

    These structures reveal the flexibility of a tyrosine side-chain involved in locking the adenine ring after ATP binding. The essential role of this tyrosine was confirmed by mutation to Ala leading to a drastic loss of enzymatic activity. You'll be in good company.