Three-dimensional Non-close-packed Structures Out Of Nonequilibrium Self-assembly

Non-close-packed structures,such as diamond lattice,are a class of materials with low packing fraction.With the development of photonic technology,non-close-packed structures with optical wavelength-sized building blocks(of the similar size with col-loid)arranged in cubic diamond lattice,were identified as an ideal photonic crystal possessing full three-dimensional photonic band gap.However,without the help of co-valent or hydrogen bonding at the molecular scale,low filling fraction and mechanical instability of dilute colloidal solution announce the notorious difficulty for the non-close-packed formation using crystallization.Recently,it was reported that systems d-welling in nonequilibrium steady state with time-oscillating interaction could produce nontrivial ordered structures which cannot emerge under fixed interaction.Inspired by such nonequilibrium procedure,namely dissipative self-assembly,we seek to find out a potential technique for three-dimensional non-close-packed formation in a similar way and to understand the nature underlying those phenomena.In this thesis,by simulation tools,we develop the pH-oscillating method into three-dimensional case of oppositely charged particles whose magnitude of charge is responsive to the pH of the solution,and study its emergent behaviors.First,in the frame of the LAMMPS code(Large-scale Atomic/Molecular Massively Parallel Sim-ulator),we adopt a simulation procedure which combines the overdamped Langevin dynamics and the NPT ensemble,to give a better evaluation toward the bulk proper-ties of such system.This simulation method was attested by being applied into two-dimensional cases and those results served an agreeable match with that the former study had given.Then,considering the limit of fast pH-oscillation where the time-dependent in-teraction can be approximated by a time-averaged formula,we find the pH-oscillating amplitude introduces a new tunable dimension,strength ratio between repulsion and attraction,to steer the behaviors of oppositely charged particles.To explore phase behaviors underneath such dimension,simulations are implemented and various non-close-packed structures,i.e.,graphite-like structure and diamond structure,are found stable in the parameter range we explore.Combining with Madelung energy analysis,we further demonstrate manipulating that dimension is an effective way to fabricate three-dimensional non-close-packed crystals.Moreover,among disordered structures,some intriguing phenomena are also witnessed under the effect of the strength ratio,including hyperuniformity and nonmonotonic diffusion.Conclusively,our simulations expand our understanding toward non-close-packed fabrication and provide a potential route for synthesizing novel three-dimensional non-close-packed structures,which has proven to be remarkably difficult from nano-and microscale particles by means of equilibrium self-assembly.