John Murphy profiles the developer of the Quantum Theory of Atoms in Molecules
Albert Einstein once famously said: 'If A equals success, then the formula is: A equals X plus Y plus Z. X is work. Y is play. Z is keep your mouth shut.' While Richard Bader has plenty of X and Y, it is probably a lack of Z that has withheld from him over the years the recognition that many feel he truly deserves.
As a young chemist with excellent prospects, he set out to find out how chemistry actually worked. His resulting theory is one of the most widely quoted, with more than 13,000 citations of his major papers. But when he first opened his mouth, and challenged a huge body of accepted wisdom, he discovered that the scientific world was not as receptive as it likes to think it is. His career has been marred by refusals of journals to publish his papers, and some believe that he has been overlooked for a Nobel Prize because he rocked the establishment too much.
His crime was to develop the 'Quantum Theory of Atoms in Molecules' at a time when chemistry was dominated by other ideas. He found that it was possible to predict the properties of molecules simply by adding up the properties of the constituent atoms. His research group developed the widely used AMIPAC program, although others have implemented his theory in other software packages. These mean that almost anything that a chemist can do in a wet laboratory can be done within a computer.
Fortunately he was backed by McMaster University in Ontario and, ironically, now that he has retired he is beginning to get the recognition that many believe he deserves.
'I think he deserves a Nobel Prize,' said Cherif Matta from the University of Toronto, a former research student of Bader. 'Chemistry had always been dominated by the theory that atoms overlap and this comes from molecular orbital theory where orbitals overlap. In molecules you do not have atomic orbitals any more, but people still like to think in these terms.
'Most importantly, Bader extended quantum mechanics to apply to parts of a system: it makes it possible to cut through the electron density and leave the laws of quantum mechanics intact. This is a very fundamental thing and that is why I believe there is a Nobel Prize there.
'But he has antagonised some people from the establishment, because when you come up with a new way of seeing things, there are people who object. It takes time to change people's minds and they are beginning to change now.'
Matta does admit to some small bias: he regards Bader as a good friend who was very kind and supportive as a PhD supervisor. He also says he is a passionate and inspirational figure, who still loves teaching even though he has retired.
Bader was born in Kitchener, Ontario. His father worked at a meat packing plant where Bader worked during summers - pulling the toenails out of the pigs. One day his father came up to him at work and told him that he had won a scholarship to nearby McMaster University.
'Right, I said. I quit - because it was an awful job,' Bader remembers. ' "No you are not quitting," my father replied. That is one thing I learned from my father, never to quit.' Bader did well at McMaster and earned a Bachelors and then a Masters Degree. Chemistry was his major but he was always interested in the physics behind it. He applied to and was accepted at MIT to work with Gardner Swain on reaction mechanisms for his PhD.
Bader said: 'We had a lot of deep discussions, and it started to occur to me that chemistry was in a real bind because we had this very powerful molecular structure hypothesis that came from the cauldron of experimental physics. But everyone had their own dictionary - different people had a different idea of what a bond was. We were trying to do science with everyone using their own private dictionary. I decided that when I left, I would make it my goal to find the physical basis of chemistry.'
He won an international fellowship to study at Cambridge University under Christopher Longuet-Higgins, which was an important experience.
Bader said: 'He was quite a man; he could reduce people to tears in 30 seconds. But it was tremendous training because he could not stand what he called "fuzzy thinking". So I had to learn theory. When I first met him he gave me the titles of two books I should read and said: "When you have read these two books, then maybe we can talk again." '
It was in these books that he found out about theories of electron density, and from then on became convinced that electron density was the vehicle for carrying chemical information. 'Longuet-Higgins pooh-poohed my theory and said it would never amount to anything.' This was to become a common theme in Bader's life.
'When I went to Cambridge I decided I was not going to do orbitals; this is all arbitrary. You have no idea of the trouble I have had publishing papers,' said Bader. 'Referees would sit on them. They could never disprove anything that I said, because I based everything on physics and on observations. They still sit on my papers. Since they can't turn it down, they just sit on it. But in the end I knew I would win, and now I have won, and I am one of the most widely-quoted chemists in the world. It has been a long hard fight. I've had a hell of a life, but it's been really great.'
He wanted to return to Canada, in fact to McMaster, but there was no opening, so he took up a post in the University of Ottawa until a job came up in 1963 at McMaster. He devoted his research to theoretical chemistry, and started working on the extensions of quantum theory advanced by Richard Feynman and Julian Schwinger.
Bader's key publications did not come until 1990, at the age of 59, when he published the book Atoms in Molecules, a Quantum Theory, in which he brought his researches together into a single theory. Why did it take him so long?
'Well, remember I started off as an organic chemist, and I had to learn all of this physics. In my work I quote Schroedinger, Schwinger, Dirac and Feynman because they are the only references I need. My theory is based on the physics.'
Bader talks quickly, with excitement and passion, about his theories. He is almost like a politician trying to win over a voter to his cause. He wants you to back him against the forces of darkness. His experiences at the hands of the establishment have clearly had an effect, because he talks about those with opposing theories as 'orbital twits'. He sees himself almost at war with fellow chemists who have been telling him he is wrong all his life.
He formally retired in 1997, but that was by no means the end of the story. Bader continues with his work and in fact the number of citations his work has been getting has increased since his retirement. Although in his 70s now, he is sure he will win in the end.
'There is going to be a final stand-off between these people who use orbitals and those who use electron density. I can't understand why everyone doesn't say, "hey, let's do it", but then they will have to give up all the nonsense that they have been doing. You show me any orbital model, and I'll show you how it either violates the laws of physics or it's totally arbitrary. I can't understand these people; they are not scientists. The problem is with paradigms: they are very hard to shift. People like Pople are going to die before they ever admit that I am right.
'Pople was at Cambridge when I was there, and I used to give him a really hard time about orbitals. All he does now is compute things. He shared a Nobel Prize for chemistry because of the programs he wrote that allow people to compute approximate wave functions for complicated systems.
'He says that anybody who spends their time trying to explain chemistry is wasting their time; the only thing that is important is calculating something. That's ridiculous; if you calculate something, you need to understand it. Not only that, but the physics of an open system that we have ended up with has allowed us to ask new questions that we were not able to ask before.
'I hope you don't get the impression that I'm bitter. I'm not bitter, I just want to give you some idea of the struggle that I have had along the way.'
If Bader's father were alive today, there is no doubt that he would be proud of his son. He certainly is not a quitter.
BSc, McMaster University, Hamilton, Ontario
MSc, McMaster University, Hamilton, Ontario
Postdoctoral Fellow, MIT
Postdoctoral Fellow, Cambridge University
Assistant Professor, Department of Chemistry, University of Ottawa
Associate Professor, Department of Chemistry, University of Ottawa
Associate Professor, Department of Chemistry, McMaster University, Hamilton, Ontario
Professor, Department of Chemistry, McMaster University, Hamilton, Ontario
Emeritus Professor, Department of Chemistry, McMaster University, Hamilton, Ontario