Intermolecular Interactions In Molecular Crystals Research Articles

Charge density based classification of intermolecular interactions in molecular crystals

Evaluation of intermolecular interactions in terms of both experimental and theoretical charge density analyses has produced a unified picture with which to classify strong and weak hydrogen bonds, along with van der Waals interactions, into three regions.

Novel tools for visualizing and exploring intermolecular interactions in molecular crystals

A new way of exploring packing modes and intermolecular interactions in molecular crystals is described, using Hirshfeld surfaces to partition crystal space. These molecular Hirshfeld surfaces, so named because they derive from Hirshfeld's stockholder partitioning, divide the crystal into regions where the electron distribution of a sum of spherical atoms for the molecule (the promolecule) dominates the corresponding sum over the crystal (the procrystal). These surfaces reflect intermolecular interactions in a novel visual manner, offering a previously unseen picture of molecular shape in a crystalline environment. Surface features characteristic of different types of intermolecular interactions can be identified, and such features can be revealed by colour coding distances from the surface to the nearest atom exterior or interior to the surface, or by functions of the principal surface curvatures. These simple devices provide a striking and immediate picture of the types of interactions present, and even reflect their relative strengths from molecule to molecule. A complementary two-dimensional mapping is also presented, which summarizes quantitatively the types of intermolecular contacts experienced by molecules in the bulk and presents this information in a convenient colour plot. This paper describes the use of these tools in the compilation of a pictorial glossary of intermolecular interactions, using identifiable patterns of interaction between small molecules to rationalize the often complex mix of interactions displayed by large molecules.

Fingerprinting intermolecular interactions in molecular crystals

We have recently described a remarkable new way of exploring packing modes and intermolecular interactions in molecular crystals using a novel partitioning of crystal space. These molecular Hirshfeld surfaces reflect intermolecular interactions in a novel visual manner, offering a hitherto unseen picture of molecular shape in a crystalline environment. The surfaces encode information about all intermolecular interactions simultaneously, but sophisticated interactive graphics are required in order to extract the information most efficiently. To overcome this we have devised a two-dimensional mapping which summarizes quantitatively the nature and type of intermolecular interaction experienced by a molecule in the bulk, and presents it in a convenient graphical format. The mapping takes advantage of the triangulation of the Hirshfeld surfaces, and plots the fraction of points on the surface as a function of the closest distances from the point to nuclei inside and outside the surface. In this manner all interaction types (for example, hydrogen bonding, close and distant van der Waals contacts, C–H⋯π interactions, π–π stacking) are readily identifiable, and it becomes a straightforward matter to classify molecular crystals by the nature of interactions, and to rapidly identify similarities and differences which can become obscured when examining crystal packing diagrams. These plots are a novel visual representation of all the intermolecular interactions simultaneously, and are unique for a given crystal structure and polymorph. Applications to a wide variety of molecular crystals and intermolecular interactions are presented, including polymorphic systems, as well as crystals where Z′ > 1.

Frontier trends in the prediction of vapour pressure of metal-organic precursors

A quantitative approach to predictions of the volatility of metal-organic precursors has been developed. The proposed concept is based on up-to-date notions concerning the character of intermolecular interactions in molecular crystals allowing for the specific features of the molecular and electronic structure of metal-organic precursors. Using the data on the crystal and molecular structure of the metal-organic precursors within the frames of the methods of statistical thermodynamics and molecular physics, we have built the models for calculating the enthalpy and entropy of crystal-vapour phase transitions starting from the potentials of interatomic interactions. The temperature dependence of vapour pressure has been calculated for various precursors with known crystal and molecular structure. The calculated and experimental data on vapor pressure have been compared. The behaviour peculiarities of thermodynamic functions depending on the features of molecular structure of metal-organic precursors and their packing in crystals have been revealed. Information content and predictability of the proposed model notions for the forecast of vapour pressure for metal-organic precursors have been demonstrated.

Prediction of crystal structures

The atom–atom potential method has been demonstrated to quantify intermolecular interactions in molecular crystals of organometallic compounds. A sufficiently general minimization program with a robust steepest-descent algorithm has been used successfully to show that experimentally determined crystal structures correspond to energy minima. The algorithm may be used to predict hitherto unknown crystal structures starting from random packings.

Absolute Raman intensities of lattice modes‐investigation of intermolecular interactions in molecular crystals

AbstractAn investigation has been carried out on the correlation between intermolecular interactions and absolute Raman intensities of lattice modes. The analysis was performed by comparing absolute Raman intensities (measured using crystalline powders) with it could be shown that, in geoerd, the oriented‐gas model is inadequate for the description of the properties of molecular crystals. Large discrepancies in the model could be revealed for modes with both librational and translational character. The discrepancies depend strongly on the intermolecular interactions.

Zero point oscillation energy effect on plastic deformation in solidified gases

AbstractAn investigation is made of the deformation of molecular crystals of methane and argon under the conditions of tension and stress relaxation. The Peierls barriers are shown to be the main obstacles for dislocation movement in these crystals in a wide low‐temperature range. The result obtained is in good agreement with data determined for hydrogen, deuterium, and ammonium and is discussed in terms of the peculiarities of intermolecular interactions in molecular crystals. In particular, it is shown, that the contribution of zeropoint oscillation energy to the bonding energy increases with decreasing temperature at which the transition from the Peierls mechanism to higher energy mechanism occurs.