We report a computational method to investigate the mechanism through which the solvent interacts with the crystal surfaces during the crystal growth process. We have considered the role of the internal, crystal-solution interfacial structure and external growth environments affecting crystal growth to predict the growth morphology by calculating relative growth rate of different crystal faces. The interfacial structure and bonding energies of solute and solvent molecules of faces having different crystallographic orientations are obtained using periodic first-principles density functional method. The effects of molecular orientation of growth units and surface relaxation of the habit faces have also been considered in order to identify the adsorption of rate-determining molecules to different faces of crystals for their growth. On the basis of the analysis of interfacial structure and external growth environment, the expression for growth rates relating the level of supersaturation, temperature, solubility, bonding energies of solute− surface, solvent−surface, and the rate of growth has been derived. The method is applied to study growth morphology of two molecular crystals, namely, urea and β-succinic acid crystals from vapor and different solvents. The results obtained from calculations match well with the corresponding available experimental data. The remarkable agreement between the predicted growth shapes and the corresponding experimental results allow us to understand the role played by solvents and external growth factors on growth morphologies of molecular crystals.

We report a computational approach to elucidate the role of external growth parameters, additives, solvents, and their concentration to predict the steady-state crystal growth morphology. The developed growth rate expression relates the kinetic and thermodynamic aspects of the adsorption of these species on flat faces of crystals. Searches for stable solvent−surface interfacial structures are performed by ab initio evolutionary algorithm to accurately determine the adsorption energies of solvent at crystal surfaces. The calculations of solute−surface, solvent−surface, and additive−surface energetics have been obtained using periodic first-principles dispersion corrected density functional theory. The approach has been successfully applied to the case of urea crystal to study the aqueous growth morphology with and without addition of additive such as biuret. Different step configurations along 2-D lattice vector and molecular orientations are examined before obtaining the rate-determining adsorption energies for solute. In the absence of biuret, we predict needle-like shapes of urea crystal from aqueous solution as functions of supersaturation and temperature, which are in good agreement with the experimental data. The results show that the growth of the fast-growing (001) face is significantly retarded when biuret is present. On the other hand, addition of biuret hardly affects the growth of (110) face. The adsorption energy and, hence, surface coverage of biuret molecules at (001), (111), and (1̅ 1̅ 1̅ ) faces are significantly higher than that of (110) face. On (001), (111), and (1̅ 1̅ 1̅ ) faces, the biuret molecule formed stronger lateral bonds with the surface; on the (110) face instead, the biuret molecule has smaller adsorption energy as compared to water at the lattice sites exposed on this face.

A facile hydrothermal synthesis route was explored to obtain various nanostructures of Co oxide for applications in electrocatalytic water-splitting. The effect of reaction time and metal precursor ions on the morphology of synthesized nanostructures was studied in detail with the aid of a scanning electron microscope. By systematic optimization of the synthesis parameters, Co oxide nanostructures with single dimensionality were obtained in the form of 0D nanoparticles (NPs), 1D nanowires (NWs), 2D nanosheets (NSs) and 3D nanocrystals (NCs). The effectiveness of the developed nanostructures towards oxygen evolution reaction (OER) was studied and a promising OER activity was recorded for all the samples. Amongst all the developed catalysts, Co(OH)2 NPs showed the lowest overpotential of 339 mV to achieve a current density of 10 mA cm-2, which is even lower than that of noble-metal oxides such as the commercial RuO2 catalyst (370 mV). The specific effect of different parameters such as BET surface area, phase, crystallographic orientation of surface lattice planes, electroactive surface area and surface active species on the OER performance was studied. It was found that the Co3O4 phase is more active for the OER, compared to the Co(OH)2 phase. However, Co(OH)2 NPs showed the best OER performance owing to their higher BET surface area, thereby underlining the significance of the catalyst surface area. The effect of the number of active surface atoms was demonstrated by estimating the electroactive surface area of all Co3O4 nanostructures. It was also shown that the formation of CoO2 species (Co(IV)) on the surface is more beneficial for the OER as compared to the formation of CoOOH species (Co(III)). Finally, the robustness of the developed Co3O4 nanostructures was established by performing a recycling test for the OER (1000 cycles) and the observed change in the catalytic activity was correlated with morphological variation.

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