Assist. Professor Yuthana Tantirungrotechai, Ph.D. Thailand Young Scientist Award Year 2005 Dr. Yuthana Tantirungrotechai completed Ph.D. in Theoretical Chemistry form University of Cambridge, UK in 1999. He has been involved in basic research on the applications of quantum chemical techniques for the understanding of molecular properties and the intermolecular interaction since his post-graduate studies. The electric and magnetic properties at the molecular level provide key information for the design, fabrication and applications of nanostructured materials. Chemists use the knowledge of the intermolecular interation to design the catalytic center and the reaction mechanism. He investigated the effect of an external electric field on the change of molecular structure which is very important for the design of molecular switch and the lock-and-key principle in the drug-receptor interaction. The effect of neighboring molecules such as the ring current and the hydrogen bonding on the change of magnetic properties is successfully explained by using the classical model. His assessment of the currently-developed density functional theory was acknowledged and mentioned in international textbooks.