Solid State Analysis - Crystal Structure, Chemical Effects and Behaviour, Polymorph Prediction

Solid State Properties

Analysis of published crystal structures can be used to give a first indication of preferred molecular orientations, packing motifs and non-bonded interactions. Molecular modelling techniques can be applied to help understand chemical effects and behaviour at the molecular level. Using the most sophisticated software currently available, it is possible to start to predict how individual molecules might pack together and rank possible polymorphic forms based on their predicted energies.

To find out more on each of these areas, see below:

For information on experimental crystallography services see:

Crystal Structure Analysis

The number of published and archived crystal structures, obtained using both X-ray and neutron diffraction methods, is rapidly increasing. Crystal structure databases can be searched and mined to analyse molecular conformation and packing motifs. Using knowledge bases extracted from subsets of these databases, intermolecular interactions can be studied for a wide variety of interacting chemical groups.

Techniques applied for crystal structure analysis include:

Analysis of molecule conformation

Identification of packing motifs

Study of types and preferred orientations of intermolecular interactions

Simulation of X-ray powder diffraction patterns

Modelling of Chemical Effects and Behaviour

Molecular modelling techniques such as molecular mechanics, molecular dynamics and ab initio methods can be used to help understand chemical effects and behavior at the molecular level. Molecules can be investigated in the gas phase, in solution, or in the solid state.

Techniques applied in this area include:

Molecular geometry optimisation

Molecular conformational analysis

Chemical reaction analysis via energetics

Charge distribution analysis

Molecular dynamics simulations for studies of:

molecule - molecule interactions

molecule - solvent interactions

molecule - surface interactions

Polymorph Prediction

Using some of the most sophisticated molecular modelling software currently available, it is possible to start to investigate and predict how individual molecules might pack together in the solid state. By generating a large number of possible packing motifs in many different space groups and then ranking each of these in terms of lattice energy, an indication of which polymorphic forms might be expected experimentally cn be obtained.

Polymorph prediction involves the following steps:

Generation of possible structures using a simulated annealing process
Geometry optimisation of each possible structure
Clustering and clean up to remove duplicate structures
Ranking of structures by lattice energy