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By Lynne Robinson
Pushing Boundaries: Honoring the Contributions of Vasek Vitek|
Posted on: 7/6/2009 12:00:00 AM... Vasek Vitek was exploring largely uncharted territory as he toiled on atomistic simulation of dislocations and stacking faults in the wee hours of the morning at Oxford University in the late 1960s. At that time, one computer served the entire university, and as a post doctoral fellow, the only way Vitek could ensure access to it for his studies was to “spend a lot of nights there,” sometimes not going to bed until 6 a.m. to snatch a few hours sleep.
What emerged from Vitek’s marathon late-night sessions on, by present standards, relatively primitive equipment would help lay the groundwork for today’s field of computational materials science. In the words of his first Ph.D. student, Adrian Sutton, “When Vasek began his simulations of screw dislocations in the sixties, there were very few people anywhere in the world engaged in such work. Metallurgy, as materials science was known then, was largely an empirical subject, dominated by experimentalists with a few theorists working with pencils and paper. Today, we regard computational materials science as one of the central pillars of the subject, and there are thousands of people engaged in the pursuit. Vasek has contributed directly to that transformation through his own seminal research. But he has also mentored others who have gone on to become leaders of the field in their own right. He is a father figure in computational materials science.”
To recognize Vitek’s many influential contributions to materials science and engineering, Sutton, currently professor of Nanotechnology at Imperial College London, and a number of other colleagues are organizing the “The Vasek Vitek Honorary Symposium on Crystal Defects, Computational Materials Science, and Applications,” scheduled for the 2010 TMS Annual Meeting to be held February 14–18 in Seattle, Washington.
“Our goal is to bring together scientists from across the areas of materials science that have been impacted by Professor Vitek's work,” said David J. Srolovitz, symposium co-organizer, Dean at Yeshiva College in New York, and Vitek’s second Ph.D. student. “While the areas are diverse, the approach, the methodology, and the type of thinking that he has taught all of us in this field are common across the topics we cover in this symposium. It is our hope that these commonalities are brought into sharp focus by examining Professor Vitek's contribution as a whole.”
Abstracts for this symposium are being accepted through July 15, 2009. Access this link for additional information or to submit an abstract.
It was as a post doc at Oxford that Vitek wrote his most cited paper, which introduced the concept of the gamma-surface (V. Vitek, Phil. Mag. 18, (1968) p. 773). “This is a theoretical construct so fundamental to the understanding of the mechanical properties of materials that it is taught routinely during undergraduate degrees,” said Marc Cawkwell, a recent Ph.D. student of Vitek’s who is currently working at Los Alamos National Laboratory.
Vitek’s subsequent pioneering studies “paved the way for the many subsequent atomistic simulations of the structure and motion of dislocations in b.c.c. metals, by Vitek and others, using more realistic potentials for transition metals and ab-initio computation,” said Sir Peter Hirsch, Emeritus Professor of Metallurgy at Oxford, who was the Isaac Wolfson Professor of Metallurgy and head of the department at the university when Vitek joined it in 1967. “These studies have greatly advanced our understanding of the mechanisms controlling the yield stress of these metals.”
Hirsch said that Vitek and his colleagues extended these types of simulations to dislocations in L12 alloys, like Ni3Al, leading to the Paidar, Pope and Vitek theory for the anomalous temperature dependence of the yield stress and related orientational dependences in L12 compounds (V. Paidar, D.P. Pope and V. Vitek, Acta Metall. 32, (1984) p. 435).
“Vitek has also made many outstanding contributions to the atomistic modeling of grain boundary structure, including grain boundary dislocations, and also to the question of structural multiplicity,” Hirsch continued. “In a major modeling study of high angle boundaries in cubic metals, he and Sutton determined the nature of the structure of such boundaries, providing evidence for a description in terms of fundamental structural units (A.P. Sutton and V. Vitek, Phil. Trans. Roy. Soc. A309, (1983) pp. 1, 37, 55).”
Vitek, a 1999 TMS Fellow, with Ricardo Schwarz, Los Alamos National Laboratory fellow and 2002 TMS Fellow, as they celebrate their induction into the National Academy of Engineering (Click on image to enlarge.)
Petros Sofronis, Professor and Associate Head for Mechanics Programs, University of Illinois at Urbana-Champaign, likewise described Vitek as “a path-breaker in any area of mechanical behavior of materials he has worked on,” with “seminal and novel” contributions in the area of solid mechanics.
“Professor Vitek’s work on plastic yielding of cracked solids stands out as the first attempt to tackle through elegant dislocation modeling issues of yielding and fracture under plane strain conditions,” said Sofronis. “Previous dislocation-based work on the subject had been carried out exclusively under antiplane conditions and results under plane strain conditions were needed to establish elastoplastic failure criteria in terms of macroscopic parameters such as the J-integral or the crack tip opening displacement. Professor Vitek’s work provided many insights into the field of nonlinear plastic fracture which were verified later by large-strain elastoplastic finite element analysis.
“By way of example, Professor Vitek identified the complexity of the relationship between the J-integral and the crack tip opening displacement in plane strain, in contrast to the corresponding simple relationship governing antiplane shear,” Sofronis continued. “In the area of creep fracture through grain boundary cavitation, Professor Vitek modeled the materials science aspects of the problem by employing dislocation theory to explain phenomena such as the effect of stress relaxation on material plating into grain boundaries through diffusion. Indeed, Professor Vitek, whose natural intuition is really phenomenal, is a master of the field of solid mechanics. His relevant publications demonstrate his spectacular ability to cross discipline boundaries.”
Vitek’s most recent work has focused on the development and modeling application of bond-order-potentials that include mixed nearly free electron and covalent type bonding in transition metals and alloys. He has been carrying out these studies in collaboration with D.G. Pettifor, the current Isaac Wolfson Professor of Metallurgy at Oxford, who conceived the physical framework of these potentials.
“Vitek’s characteristic contribution has been to show how computer simulations on the atomistic scale can be used to further our understanding of structures of defects and of mechanical properties of metals and alloys, opening a new and powerful approach in this field,” said Hirsch. “He is, without doubt, a world leader in this area, and his work has had considerable impact.”
A Legacy of Learning
According to many of Vitek’s colleagues through the years, perhaps his greatest impact has been on the numerous young scientists who have studied with him. Said Cawkwell, “Vasek's real skill in supervising students is that he takes a very hands-off approach. He allows his students to explore and solve a problem for themselves—He really just guides the student in the right direction, often without the student's knowledge, and relies heavily on the student's self-motivation to ensure the work gets done. In this way, people who have graduated from his group are very well equipped to take leadership roles in science.”
“Professor Vitek showed me how to think as a scientist, how to balance theory and computation, and how to focus on details while keeping a view of the big picture,” said Srolovitz. “He showed me how a scientist should approach his science, approach his colleagues, and mentor students. I try to practice all of these lessons on a daily basis.”
Cawkwell echoed Srolovitz’s comments. “Vasek taught me to be patient in science and research since the problems we are tackling are very difficult and it is silly to expect that such things can be solved in a short period of time,” he said. “Vasek has been working on similar problems for his whole career—He has resisted jumping from one fashion to the next. It takes a strong personality to avoid the low hanging fruit when pursuing the major and most difficult problems in materials science. In this way, he has certainly gained the respect of his peers.”
Respect of peers has been reflected in numerous accolades showered upon Vitek, a Professor at the University of Pennsylvania since 1978. These have included being named a TMS Fellow in 1999, the organization’s highest recognition, and being inducted into the National Academy of Engineering in 2006.
"A Breakthrough Is Something You Don't See Coming"
Vitek attributes the path that his career has taken to the mentors and colleagues who have helped shape him over the years. For instance, he credits Franta Kroupa, his Ph.D. advisor at the Czechoslovak Academy of Sciences, for introducing him to the study of the mechanical behavior of materials. “Dr. Kroupa said that, with advancements in condensed matter physics and computers, we should be able to get to atomic level studies of materials deformation,” recalled Vitek. “He encouraged me to go in this direction, which I did.” Vitek also points to the influence of J.W. Christian, who advised him during his post doctoral studies at Oxford and with whom he co-authored an extensive review on dislocation theory. “Professor Christian had an immense impact on my scientific thinking as well as my approach to the education of graduate students,” said Vitek. “It was his style that helped me develop really independent thinking—to not follow fashions in science.” On a more personal note, Vitek said he “is deeply indebted” to Sir Peter Hirsch, “not only for profound scientific advice, but also for his help after the Soviet invasion of Czechoslovakia that impacted my whole life.”
After having contributed so vigorously to the growth and knowledge base of materials science and engineering over the years, Vitek said that predicting truly new directions in the field is “almost impossible.”
“In research, if you can predict what will happen, it’s not that exciting,” he said. “In general, I know that advances in computers will obviously enable us to do many more things than can be done now. I also think there needs to be much more progress in materials related to making energy as green as possible, particularly in understanding material problems associated with nuclear energy. But, it is impossible to say what the next exciting advance will be.
“If I were able to tell you, it would not be a breakthrough,” Vitek continued. “A breakthrough is something that you don’t see coming.”
Visit the TMS 2010 Web site for additional information on the TMS 2010 Annual Meeting and the Vasek Vitek Honorary Symposium on Crystal Defects, Computational Materials Science, and Applications.
Lynne Robinson is the news and feature writer for Materials Technology@TMS.
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