LAMARCKIAN EVOLUTIONARY ALGORITHM WITH FLEXIBILITY AND CONTINUOUS SCHEME FOR CRYSTAL STRUCTURE PREDICTIONS

• Main Author: MAHMUD HANNA (NIM: 20909303); Pembimbing : Muhamad A. Martoprawiro, Ph.D., ATHIYA
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/15078
• Institution: Institut Teknologi Bandung

Crystal structure prediction using Lamarckian evolutionary algorithm methods have been improved by applying operators <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> exibility and continuous scheme. In this research, some new concepts of operators exibility are introduced and implemented. Basic evolutionary operators acted as building block of actual operators are then composed such that very <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> exible composition operators can be generated to do procreation. Continuous scheme is also implemented in this <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> method. These two improvements are aimed to increase self-learning power of this method to predict crystal structures at high-pressure. To construct exible operators, applied evolutionary operators were made by composition of basic evolutionary operators. There are five basic evolutionary <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> operators. Crossover operator combines 8 crystal structures into one new crystal structure. Lattice vector permutation operator exchanges lattice constants. Lattice point permutation operator exchanges position of two different atoms. Lattice vector mutation operator distorts lattice vector of crystal structures. Lattice point mutation operator shifts lattice points randomly. Some applications were carried out using this modified method on silicon <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> (Si) at 160, 450, and 900 kbar, phosphorus (P) at 900, and 2070 kbar, titanium (Ti) and sodium chloride (NaCl) at ambient pressure. In this research, ab-initio calculation method was used for local optimization method. The simulations were performed in two steps, i.e. structure seeking step to find correct crystal structure type and enhancement step to enhance accuracy of calculation of <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> crystal structure parameters. Results obtained from these simulations are in very good agreement with experimental research works.