Krishnan Raghavachari, Distinguished Alumnus Awardee 2014, talks about his life at and after IIT Madras. He graduated with a masters in Chemistry at 1975.He is currently a Distinguished  Professor at the Department of  Chemistry , Indiana University.

I was born and raised in Madras, and as is customary, I was simply known as R. Krishnan all through high school and college. It was only much later in the United States I was referred by my full name of Krishnan Raghavachari. As a student in high school, I was strongly drawn to mathematics and science. I faced my first key decision in my life when I took the JEE exam to enter IIT in 1970, and achieved All India rank #1!.
Electronics was the hot area in IIT then, and my friends suggested that I make it my chosen field of study.  I did not, however, have much exposure to Electronics or any other branch of Engineering.  Instead I clearly knew that I was very interested in Chemistry. I decided that I would pursue science, and joined Vivekananda College in Madras for a B.Sc. in Chemistry. I had received the National Science Talent Scholarship that allowed me to take part in Summer Schools and do some special activities in Chemistry. However, I used to wonder for several years if I had made a rash decision by not joining IIT and choosing Science instead.

I finished my B.Sc. in Chemistry in 1973 and had my second chance to join IIT. I received top placement scores in the M.Sc. entrance test and decided to join Madras IIT for my master’s degree in Chemistry. I stayed in Mandakini hostel and spent two happy years roaming around the wonderful IIT campus from 1973-1975. They were important formative years in the development of my interest in chemistry. We had many outstanding Professors in various branches of chemistry. My interactions with them led me to discover my interest in Physical Chemistry, and in particular the subfield of theoretical chemistry related to the electronic structures of atoms and molecules. The use of computers in chemistry (computational chemistry) was beginning to emerge, and IIT Madras had acquired an IBM-370 computer, one of the very few mainframe computers in India. However, computer time was precious, and we had to stand in line each morning to be allocated a few minutes of computer time later that day! I did my M.Sc. project with Prof. V. Subramanian to explore theoretical and computational chemistry using semi-empirical methods. I learnt Fortran programming and modified some previous models while receiving  guidance from J. Chandrasekhar, a graduate student in IIT Madras, who went on to have an outstanding career himself. I decided to apply for graduate schools in the United States to obtain a Ph.D. in chemistry.

Prof. Subramanian’s guidance in choosing graduate schools was critical to my later success. He suggested that I apply to Carnegie-Mellon University to work with Prof. John Pople, who had developed much of the semi-empirical models that I was working with. However, I did not know how much of a giant he was in the field of theoretical chemistry, particularly on the applications of quantum mechanics and the use of mathematical and computational methods to solve problems in chemistry (quantum chemistry). Prof. Pople went on to receive the Nobel Prize in Chemistry in 1998, and was later knighted by the British Queen to become Sir John Pople. While I was receiving admissions and fellowships at Universities ranked higher (in chemistry) than Carnegie-Mellon University, Prof. Subramanian was influential in impressing upon me the importance of the role of the mentor and thesis advisor during the pursuit of a Ph.D. degree. I was also fortunate that Prof. Pople was sufficiently impressed with my application that I was offered a special “John Christian Warner Fellowship” in Chemistry at Carnegie-Mellon University to work with him.

My time at Carnegie-Mellon University was very special. Prof. Pople offered me one of the most important and challenging problems in the field at that time as my thesis topic, namely the development of electron correlation methods in quantum chemistry. This problem relates to an accurate theoretical description of electron-electron interactions, intimately tied to the chemical bonding responsible for the structures and properties of molecules and materials. With Prof. Pople’s help and the mentorship I received from several senior members of his group (particularly Dr. Seeger), I developed several new methods and algorithms (such as fourth order perturbation theory) that are widely used in the scientific literature today. A particularly important aspect was the treatment of three-electron correlations (triple excitations) that are crucial in any highly accurate method in quantum chemistry.

My personal life also had an important milestone during that period. I married one of my M.Sc. classmates from IIT Madras (Akola) who came to join me in 1976 to pursue her Ph.D. at Carnegie-Mellon University! We were married in 1977 while still at a fairly early stage of the Graduate School, and have been happily married for nearly 37 years at this writing. We have two lovely daughters (Ranjani and Meera) and have just become proud grandparents in 2014 with the birth of our grandson Naveen! Only after meeting Akola in 1973 was I convinced that not joining IIT in 1970 but waiting to join until 1973 was the right decision for me!

I worked in another important area of quantum chemistry in the second half of my Ph.D. This was the area of developing gradient methods in quantum chemistry that make it possible to efficiently calculate accurate structures and spectroscopic properties of molecules. With the support of some senior associates (particularly Dr. Schlegel) we developed several new methods that led to key publications. Our papers were getting quite well known, and four of our papers were listed among the most influential papers in quantum chemistry just as I was graduating with my Ph.D. in 1980! The key to our success was Prof. Pople’s insightful and brilliant choice of important and challenging problems as research topics and his persistence in solving them in a timely manner.

I was receiving several offers as I was getting ready to graduate. I decided to join Bell Laboratories in 1981 to pursue my independent research career. I intended to be there just for a few years as a stepping stone for an academic career. But Bell Laboratories provided an incredibly stimulating scientific environment (with more than 10 Nobel Prize winners in Physics) that I ended up spending nearly 22 years there. While being exposed to advanced scientific and technological topics in an “industrial” environment, it also promoted fundamental scientific pursuits from a problem-oriented perspective, somewhat different from a typical University environment. I also received advice from many outstanding senior scientists at Bell Laboratories (Dr. Stillinger, Dr. Tully, Dr. Cardillo and others).

The first advice that was given to me at Bell Laboratories was to start projects in independent research areas that are completely different from the Ph.D. work. I still shared many interests with Prof. Pople, but I had to cut the “umbilical cord”, and work on independent topics unrelated to my previous scientific interests. I selected the emerging field of clusters to perform theoretical investigations that provided the complementary information to understand the exciting experimental work in that field. I also elected to work on silicon surface chemistry, utilizing the unique environment of Bell Laboratories, and started a long-term collaboration with Dr. Yves Chabal, a brilliant experimental surface spectroscopist. My work on clusters and surfaces was quickly getting recognition, and I was receiving invitations at Universities and Conferences. By 1986, I was promoted to be a “Distinguished” scientist at Bell Laboratories. In the meanwhile, our daughters Ranjani and Meera were born during this important period in our lives.

Several significant events happened around this time. I was still having conversations on and off with Prof. John Pople.  The theories of electron correlation were more developed but they still did not have “chemical accuracy” (accurate within 1-2 kcal/mol that is typical of the accuracy possible in many experimental measurements). In one of our conversations, he mentioned a new theory for the treatment of up to two-electron correlations (single and double excitations) but it was not accurate enough. I had thought about this for a long time and it was clear to me that a better model for three-electron correlations (triple excitations) was needed. However, a brute force treatment of their contributions was computationally prohibitive. I decided to combine my previous experience in perturbation theory to develop a novel and computationally efficient way of treating triple excitations by combining two different terms arising from their interactions with single and double excitations, respectively. My ideas turned out to be the key piece in solving this important puzzle! By 1987 it was perfectly acceptable for me to collaborate again with Prof. Pople (on a more even footing unlike the teacher-student relationship of the earlier years), since I had already established an independent successful career on other topics.  We continued to work together on several other important research areas until he passed away in 2004.

My most important paper was published in “Chemical Physics Letters” in 1989. While it was a collaborative work with Prof. Pople, it was based almost entirely on my novel treatment of triple excitations in conjunction with coupled cluster theory. This led to a method, labeled CCSD(T),  that has turned out to be so successful in its impact on our field that it is referred to as  the “gold standard of quantum chemistry”. It is so accurate for small molecules that it is frequently used as the reference (instead of experiment) to calibrate other approximate methods. Nearly 25 years after publication, it still stands as the method of choice for highly accurate calculations in quantum chemistry, and our paper has received over 4000 citations. Our 1989 paper was just reprinted in a special “Nobel Prize” issue of Chemical physics Letters in 2013.

One of my most exciting moments came in 1998 as I was driving to work in late October. I heard an announcement on my car radio that the Nobel Prize in Chemistry in 1998 was being awarded to my mentor, Prof. John Pople. I ran into my office and left a congratulatory message on his phone that he later mentioned as one of the first messages that he received that day. A more exciting moment came just a few days later when he called me and invited me to accompany him to Stockholm to participate in the Nobel Prize ceremonies! The ceremonies in December 1998 were just amazing. I participated in the grand Nobel banquet wearing “white tie and tails”, visited the Swedish Academy of Sciences, attended press conferences involving all the Nobel Laureates, and many more special events. It will always remain as one of the most memorable times in my life.

In addition to Prof. Pople’s scientific genius, he was also a visionary person with respect to the development and distribution of scientific software. He realized that the best science can only be achieved if scientific software is disseminated broadly and used by scientists with diverse ideas and backgrounds.  I was fortunate to be involved intimately with the “Gaussian” program suite, developed originally by Prof. Pople at Carnegie-Mellon University. It still stands as the most popular quantum chemistry package used by thousands of research groups around the world.  I recently had an opportunity to help in the organization of a “Gaussian Workshop” to train young Indian Scientists in the use of scientific software for chemical research. The first workshop was held jointly between CLRI and IIT Madras in January 2012 and was highly successful due to the efforts of Dr. Subramanian (CLRI) and Prof. Mangala Sunder (IIT-M). More workshops have since been conducted in other parts of India, and Indian scientists are consistently performing high quality original research in quantum chemistry and publishing papers in internationally recognized journals.

I moved to Indiana University as a Professor of Chemistry in 2002. This was the academic life I always wanted, and teaching and training young minds has been most rewarding. I enjoy teaching both large undergraduate classes with hundreds of students as well as graduate classes with just a handful of students. My Ph.D. students and post-doctoral research associates are spreading their wings and establishing their own independent careers. My collaborations have continued to flourish, and Dr. Chabal and I won the Davisson-Germer prize in surface physics given by the American Physical Society in 2009. I was fortunate to be elected as a member of the International Academy of Quantum Molecular Sciences in 2010. The year 2014 has been particularly special thus far. I was recognized earlier this year as a “Distinguished Professor” at Indiana University. The recognition as a “Distinguished Alumnus” at IIT Madras is particularly special since this is the place where my scientific career began. The various stages of my professional as well as personal life had their origin from my days at Madras IIT, marking year 2014 as the culmination of many events that have led up to this. It is a most special moment and I am most delighted to take part in the Institute Day events this year.