A molecular crystal does not have a single stiffness value. Its molecules are arranged differently along different crystallographic directions, so the same crystal can resist force strongly on one morphological facet (an exposed crystal surface) and deform or crack more easily on another. In pharmaceutical manufacturing, this can affect milling, powder handling and tablet compression, influencing whether a medicine can be produced consistently. In electronic materials, facet-specific stiffness can affect durability during manufacture and use. Laboratory nanoindentation, which presses a tiny tip into the crystal surface, remains essential, but some facets are too small or difficult to test reliably.
Researchers in the Department of Chemistry at Khalifa University developed the MechaPredict software to identify promising crystal facets and predict their mechanical response before committing to expensive experiments. MSc in Applied Chemistry student, Mubarak Almehairbi, wrote and tested the code in work conceived by Prof. Sharmarke Mohamed, Associate Professor of Chemistry and Theme Leader at the Center for Catalysis and Separations.
鈥淢echaPredict allows the high-throughput screening of the mechanical properties of crystals without doing a number of serial and time-consuming nanoindentation experiments,鈥� said Prof. Mohamed.
MechaPredict is a code that calculates the facet-specific Young鈥檚 moduli of molecular crystals, showing how stiff a chosen crystal facet is when force is applied. It turns quantum-mechanical calculations into a mechanical property that can be tested in the laboratory. During development, the team used Khalifa University鈥檚 high-performance computing (HPC) cluster to study the mechanical properties of molecular crystals in a systematic fashion.
The calculations use quantum mechanics to work out how strongly the molecules in a crystal hold on to one another. The team compared three versions of these calculations, each treating the weak attractions between molecules slightly differently. MechaPredict then combines the resulting stiffness data with the facet a user selects to calculate that facet鈥檚 Young鈥檚 modulus, a measure of how strongly it resists being deformed.
MechaPredict does its part in an instant; producing dependable input data is the demanding part. The structure of each crystal must first be refined on the computer, and working out how it responds to being pushed or pulled in every direction takes many repeated, expensive quantum-mechanical calculations. Khalifa University鈥檚 HPC cluster allowed the researchers to apply the same approach across 15 crystals, 24 facet-specific experimental measurements and all three versions of the calculation. The code was validated by comparing predictions with those measurements.
The toughest test was a blind one. Starting only from the crystal structure of L-aspartic acid, a dietary supplement, the team predicted the stiffness of its (020) facet before any measurement was made: 24.59 gigapascals (GPa). The facet was then measured in the laboratory by nanoindentation, giving 24.53 GPa with a margin of error of 卤0.56 GPa. The prediction fell well within that margin, as did the results from the other two versions of the calculation.
鈥淢echaPredict itself gives an answer within seconds. The hard part is the quantum-mechanical calculations that feed it, and without the KU HPC cluster we could not have run them for every crystal in the study,鈥� said Prof. Mohamed.
鈥淏y carefully simulating how the response of a crystal to stress changes from one facet to another, we are now in a better position to understand, for example, why some crystals crack under stress while others can withstand significant stresses before they fracture,鈥� he added.
The work was published in in 2024. A public provides releases, an installer, documentation and license-request information. MechaPredict already has several freely licensed academic users around the world. Copyright protection is under review by the relevant UAE bodies, with support from Khalifa University Enterprises Company (KUEC), the University鈥檚 technology transfer platform. The team is exploring licensing routes for commercial customers in the pharmaceutical industry who have expressed interest in licensing the code from Khalifa University. The software is being marketed and maintained by Solid Form Innovations, a spin-out company founded and led by Prof. Sharmarke Mohamed.
