Research Proposal by Robin Chang Yee Hui Proposed Research Title Material Design of III-Nitride Ternary via First Principles Calculations Literature Review Computational modeling techniques are widely employed in material science for the past two decades due to progress in computing power and simulation methodologies. Rapid decrease in the unit price of CPU power, physical memory and enormous hard disk space for scientific calculations have found their way into the mass market. There exist also at the same time commercially and non-commercially integrated software packages such as Gaussian09, ABINIT, Wien2k, VASP, LAMMPS and others. All these enables complex experiment to be carried out at relatively low cost, thus it is a numerical experiment in disguise. At its best, using appropriate physical models and the minimum pf ad hoc assumptions, computer simulations can be used as a powerful tool to guide novel experiment programmes in a fraction of time and cost of trial-and-error approaches. When being compared to experimental approach, computational technique is relatively cheap and convenient, prevalently producing interesting data and at times unearthing new materials. Computational modeling virtually covered all areas of mainstream materials science, including polymers, ceramics, semiconductors and metals. It is also a major driving force in new avenues of research, such as pharmaceutical materials science , nanotechnology and engineering , biomaterials , solid state electronics , to name a few. An emerging paradigm for accelerated materials discovery is to design new compounds in silicon using first principle calculations, and then perform experiments on the computational designed candidates. Using a computational approach to help design new materials offers several benefits that are complementary to traditional experimental-based materials discovery. One key advantage of computations is the level of control they offer compared to experiments. For example, it is often trivial in calculations to simulate the effects of chemical substitutions of or lattice strain, but achieving those same conditions experimentally could take many months of painstaking laboratory work. In addition, characterizing a material’s fundamental properties is often quicker with computations compared to experiment while still retaining excellent or acceptable accuracy. This is most apparent in recent highthroughput DFT studies in which properties of thousands of materials have been calculated in relatively short time frames, opening up the possibility for an informatics-based approach to materials design . A.R. Oganov, C.W. Glass  et. al. have developed an USPEX, a crystal structure predictor code, by implementation of the evolutionary algorithm and many other efficient variant operators. USPEX has gained success in various material structure predictions. This can be seen in the paper published such as MgSiO3 postperovskite , unexpected sodium chlorides: Na3Cl, Na2Cl, Na3Cl2, NaCl3, NaCl7 , low-energy two-dimensional boron structure , densest carbon material , and super hard graphite , to name a few. The group III nitrides (AlN, GaN and InN) represent semiconductors with direct band gaps which span the range 1.95-6.2 eV. Their ability to generate efficient electroluminescence has been the main driving force for their recent technological development. High brightness visible light-emitting diodes (LEDs) are now commercially available, a development which has transformed the market for LED-based full colour displays and which has opened the way to many other applications. On the other hand, III-nitride semiconductor ternary alloys such as aluminum indium nitride AlxIn1-xN have attracted much research interest due to its potential application in optoelectronic devise. AlxIn1-xN-based optoelectronic devices such as the adjustable energy band gap InN and AlN, light emitted diode, laser diode have been developed [12, 13]. AlxIn1-xN with 17-18% indium has also been used as strain-free cladding layer on a GaN-based laser diode structure because Al xIn1-xN and GaN are both lattice-matched . This research will be an in-depth theoretical study on wurtzite AlxIn1-xN alloys using USPEX. By varying the content of Aluminum and thus Indium, we will let USPEX to “design” the optimum crystal structure through density functional method search. Through these studies, a better understanding of the electronic behavior in wurtzite Al xIn1-xN can be obtained and this will contribute to the mankind knowledge in the condensed matter physics. Research Objectives 1 To determine/design the optimum structure for each and every possible alloy composition of AlxIn1-xN through USPEX, a crystal structure prediction module. 2 To determine the structural, electronic, optical and vibrational behaviors of the optimum structure derived (through USPEX above) using designated density functional (DFT) method. 3. To verify the theoretical investigation with the experimental data. Planned procedures/methodology 1. Initially, deeper understanding of density functional theory (DFT), USPEX, and the AlxIn1-xN must be gained (Literature Review). Al xIn1-xN (without varying the composition of Al and In) will be constructed, relaxed and optimized through dedicated DFT software. To familiarize with USPEX, result from references  and  will be reproduced. 2. For each and every possible alloy composition of AlxIn1-xN, dedicated search using USPEX will be carried. In USPEX, the optimum structure is searched using VASP, a type of plane wave-based DFT software, in variable composition mode. This will be done using computer clusters in the School of Physics where MPI capability to run parallel codes are available. 3. After the structural search of AlxIn1-xN is done, it is followed by density functional calculation (DFT) using the same DFT method in (2). Through VASP, aforementioned properties of the AlxIn1-xN alloy can be obtained. 4. Finally, the results calculated from (2) and (3) above will be verified against the experimental result which is currently in progress and work from our experimental group in the School of Physics also. References: 1. J. A. Elliott and B. C. Hancock, Pharmaceutical materials science: an active new frontier in materials research, Mater. Res. Soc. Bull., 31, 11, 869 (2006) 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. W. K. Liu, E. G. Karpov, S Zhang and H. S. 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