This thesis is written under the sincere guidance of my supervisor, Asst Prof. Zhang Dawei. I would like to express my greatest appreciation to him as being such a tremendous mentor and for all the continuous support throughout my PhD study, making me to grow as a computational chemist. I cannot imagine knowing a better advisor or mentor during my course of graduate study. The completion of this thesis will never be a success without his patience, encouragements and instructions in all ways. His advice and sharing are invaluable towards my research, career as well as the attitude of future life. Also I would like to thank Prof. Mei Ye for his help and generous in providing the source code I used in my PhD study. My colleagues in Dr. Zhang's group, Cui Jinglan, Yang Hong, Yip Yew Mun, especially Dr. Wei Caiyi, Dr. Sun Tiedong and Dr. Raudah Lazim, thanks for their immense contributions towards both my personal and professional time at NTU. Thanks for the priceless discussions, joys and friendships have ever had with them. Lastly, but never the least, a special thanks to my family. No words can express my gratefulness towards my mother, father and wife for all their sacrifices have been made for me. Their love, encouragement and support are what sustained me so far.