William Wilson Mullins, a physicist and materials scientist best known for his work on morphological changes of surfaces, interfaces, and grain boundaries, died on 22 April 2001 in Pittsburgh, Pennsylvania, after a yearlong battle with cancer.

Bill was born on 5 March 1927, in Boonville, Indiana, and grew up in Chicago. He earned the degrees of PhB (1949), MS (1951), and PhD (1955), all in physics, from the University of Chicago. His doctoral work was supervised by Cyril Smith, founder and first director of the university’s Institute for the Study of Metals. Bill’s doctoral work involved the experimental measurement of grain-boundary energies, which later led to his first scientific publication, “Magnetically Induced Grain Boundary Motion in Bismuth,” in Acta Metallurgica (1956).

In 1955, he was hired by Clarence Zener as a research scientist at the Westinghouse Research Laboratories in Pittsburgh, where he worked until 1960 in such areas as theory and topology of grain-boundary motion; thermal grooving (theory and experiments in copper in collaboration with Paul Shewmon), surface melting; and scratch decay on surfaces. His seminal papers during this period led to a much more quantitative approach to the dynamics of morphological changes of surfaces and interfaces. He was particularly proud of his generalization to curved interfaces of John von Neumann’s original n- 6 rule for growth of bubbles having flat interfaces in a twodimensional soap froth. For arbitrary shapes, Bill showed that the time rate of change of area of a grain is proportional to n- 6, where n is its number of sides, independent of shape, provided that the driving force is a lowering of isotropic interfacial free energy and that all triple junctions make local equilibrium angles of 2π /6.

While at Westinghouse Research Laboratories, Bill met one of us (Sekerka), who was fresh out of high school and had been hired as a technician, assigned to work for Bill Mullins and for Bill Tiller. This was the beginning of Sekerka’s education as a materials scientist and his discovery that Bill was a compulsive and extremely talented teacher. A scientist’s scientist, Bill had the ability to translate very complex ideas into new areas of understanding. He was careful and patient, especially in explaining concepts to people who lacked his own formal training in physics and mathematics. His four sons frequently remarked that they seldom got through dinner without a science lesson.

It is therefore not surprising that Bill soon opted for a career in academia. In 1960, he joined Carnegie Institute of Technology as an associate professor of metallurgical engineering. He headed the metallurgical engineering department from 1963 to 1966. From 1966 to 1970, he served as the dean of the college of engineering and science. At that time, he put in place procedures to promote excellence in scholarship and had the foresight to start a department of biological sciences. He also helped to guide the merger with the Mellon Institute, which led to the formation of Carnegie Mellon University and the division of the college of engineering and science into the Carnegie Institute of Technology and the Mellon College of Science. Bill subsequently gave up academic administration, both to return to his love of teaching and so that his wife could complete her doctoral studies and embark on her career as a professor of education. Bill was appointed university professor of applied science in 1985.

In his research subsequent to 1960, Bill developed several new themes. He collaborated with Sekerka during the summers of Sekerka’s graduate education to develop a theory of morphological stability during precipitation or solidification. This theory led to a quantitative foundation for cellular and dendritic growth. Bill also took an atomistic approach to phenomena such as crystal faceting and kinetics of crystal growth, including step interactions on vicinal surfaces.

In the 1970s, he developed a number of theories based on statistics, including diffusion with stochastic jump times, particle flow under gravity, and size distribution of impact craters. Much of this work was stimulated by his acute observations of natural phenomena; for example, a paper on contrast thresholds of random patterns resulted from his curiosity about the flickering patterns he saw while looking into a swimming pool.

Somewhat more exotic was Bill’s application of Newton’s laws to revolutionize an annual competition (for the amusement of students) called the faculty egg toss. The rules were very simple: Throw a raw egg as far as possible and catch it unbroken. One of us (Paxton) learned to throw (grip the end with the smaller radius) and Bill learned to catch (avoid too much rotational momentum, which is much harder to decelerate than translational momentum), resulting in throws on the order of 100 yards and winning tosses for several years.

Bill’s scientific work continued after his retirement in 1992, even through the last week before his death. Topics included variational principles for conductance in heterogeneous bodies, thermodynamics of crystalline solids, statistical self-similarity in grain growth and coarsening, and, most recently, energy barriers for shape changes of crystals with facets and nonequilibrium morphologies.

In 1963, Bill won the Mathewson Gold Medal of the American Institute of Mining, Metallurgical and Petroleum Engineers. In 1984, he was elected to the National Academy of Sciences. In 1995, he received the Materials Research Society’s highest accolade: the Von Hippel Award.

In addition to his scientific work, Bill was an active supporter of social causes, including environmental issues and world peace. A conspicuous contribution to the George McGovern presidential campaign earned Bill a place on Richard Nixon’s political enemies list—an achievement of which Bill was proud.

William Wilson Mullins