Supersaturation

Colloid

Suspension (topology)

Engineering

Chemical physics

Crystal (programming language)

Pure mathematics

Materials science

Homotopy

Single crystal

Particle size

Computer science

Chemical engineering

Physical chemistry

Thermodynamics

Physics

Seeding

Crystallization

Crystallite

Mathematics

Seed crystal

Crystallography

Chemistry

Programming language

Nucleation

Nature

The addition of small ‘seed’ particles to a supersaturated solution can greatly increase the rate at which crystals nucleate. This process is understood, at least qualitatively, when the seed has the same structure as the crystal that it spawns1,2. However, the microscopic mechanism of seeding by a ‘foreign’ substance is not well understood. Here we report numerical simulations of colloidal crystallization seeded by foreign objects. We perform Monte Carlo simulations to study how smooth spherical seeds of various sizes affect crystallization in a suspension of hard colloidal particles. We compute the free-energy barrier associated with crystal nucleation3,4. A low barrier implies that nucleation is easy. We find that to be effective crystallization promoters, the seed particles need to exceed a well-defined minimum size. Just above this size, seed particles act as crystallization ‘catalysts’ as newly formed crystallites detach from the seed. In contrast, larger seed particles remain covered by the crystallites that they spawn. This phenomenon should be experimentally observable and can have important consequences for the control of the resulting crystal size distribution.

Onset of heterogeneous crystal nucleation in colloidal suspensions