Helen Megaw

Helen Dick Megaw, crystallographer: born Dublin 1 June 1907; crystallographic scientist, Philips Lamps Ltd 1943-45; Assistant Director of Research in Crystallography, Birkbeck College, London 1945-46; Fellow, Girton College, Cambridge 1946-68, Life Fellow 1968-2002; Assistant Director of Research in Crystallography, Cavendish Laboratory, Cambridge 1949-59; Lecturer, Cambridge University 1959-72; died Ballycastle, Co Antrim 26 February 2002.

Helen Megaw was a remarkable member of one of the most important scientific disciplines of the 20th century – the field of crystallography.

In her own words, this is "the branch of science concerned with the description of the structure and properties of condensed matter in terms of the spatial relationships of atoms and interatomic forces in an extended array". The term "extended array" means a "crystal", for it is the repeated stacking of molecular units in all directions that distinguishes a crystalline solid from non-crystalline substances like glass.

Megaw was born in 1907 into a distinguished Northern Irish family: her father was a judge and Ulster politician. In addition her uncle was a director of the Indian Medical Service, one brother built the Mersey tunnel, the Dartford tunnel, the Victoria Line of the London Underground and Bankside power station, another brother was a Justice in the Court of Appeal, and one of her sisters researched diet and health in the 1930s and marriage laws in Uganda in the 1950s.

Helen Megaw decided on a scientific career, starting first at Queen's University, Belfast, before moving to Girton College, Cambridge, where she read Natural Sciences, and obtained her BA and PhD. From 1930 to 1934 she was a research student there under the great, and some would say "infamous", J.D. Bernal, along with Dorothy Crowfoot, later Hodgkin. Although she had already become interested in crystallography while at school, having read W.H. and W.L. Bragg's X-rays and Crystal Structure (1915), Bernal was a stimulating influence on her and happily confirmed her interest in crystals.

Her choice of crystallography was a wise one, because it was the one scientific discipline at the time that had already established itself as an area in which both men and women could engage on an equal basis, and she never, or rarely, was aware of any form of discrimination. She began her scientific career in the study of crystals by working on the structure of ice. The naming of an Antarctic island, Megaw Island, in her honour (at 66º55'S, 67º36'W) marked this work.

In 1934 Megaw spent a year in Vienna and then moved to work briefly under Professor Francis Simon at the Clarendon Laboratory in Oxford. Two years of schoolteaching followed before she took up a position at Philips Lamps in Mitcham, Surrey, in 1943. There she worked out the crystal structure of an important industrial material, barium titanate, which is used in capacitors, pressure sensitive devices and other electrical and optical applications. This material, which crystallises in the so-called perovskite structure, belonged to the class of materials known as ferroelectrics, originally discovered around 1935. The structure is of such significance that Megaw's name is permanently associated with it and with perovskite structures in general.

In 1945, she moved back to Birkbeck College, London, once again to work with Bernal, and in the following year she was appointed to a post in the Cavendish Laboratory, Cambridge, where she remained for the rest of her scientific life. At that time, the Cavendish was under the leadership of Sir Lawrence Bragg, and as a result Megaw found herself at a place where many well-known crystallographers would pass through. (She was there during the exciting double-helix days.) However, she remained loyal to her chosen field of mineralogy and inorganic crystals. In 1951, she was responsible for providing a number of crystal structure diagrams to the Council of Industrial Design, which were then used in the designs for the textiles used at the Festival of Britain, including in the foyer of the Regatta Restaurant.

In 1957, Megaw wrote a book entitled Ferroelectricity in Crystals, the first of its kind, and for many years this became the bible for the fast-growing international community of ferroelectricians. A second book, Crystal Structures: a working approach (1973), well illustrates her unique approach to describing the architecture of crystals. In addition to ferroelectrics, at the suggestion of W.H. Taylor, she took up an interest in the crystal structure of feldspars, the complicated materials that make up most of the earth's and moon's surface. The first structure determination had been carried out by Taylor before the Second World War, but such is their complexity, there remained a great deal of unknown science to discover.

In 1989, Megaw became the first woman to be awarded the Roebling Medal of the Mineralogical Society of America, and in 2000, at the age of 93, she was awarded an honorary degree at Queen's University, Belfast.

I first met Helen Megaw in 1969 while at an international conference in Stony Brook, New York. She was looking for a postdoctoral assistant to work on crystal structure changes with temperature in a particular complicated perovskite material. I was working at the Chemistry Department in Harvard and my interest was in the crystallography of organic compounds. I accepted Megaw's offer with some reluctance, because I felt that the subject of inorganic crystals was far too impenetrable.

She was a remarkable person to work for; formidable in some ways, but also kind and patient. She had an interesting gift: if you wanted to know what a particular crystal structure looked like from any particular direction, she could somehow turn it around in her mind and then sketch it for you – a very useful trick, in the days before computer graphics.

In 1972 I wrote a paper on the structures of perovskites, which I thought was rather clever, and sent it for publication. Eventually I received a reply with a referee's report of 20 closely written pages of criticism. I was infuriated and went to Megaw for advice. She looked carefully through the comments and agreed that they were over the top. She spent hours helping me to deal with them and I had to admit that the revised paper was much better as a result. It was a few years later that Megaw confided that she had been the original referee.

In 1972 she retired to her home in Ballycastle, Co Antrim, to pursue her other interest, gardening. She was delighted to discover the plant called Perovskia, and this quickly made its way into her garden collection. Leaves of Perovskia featured on one of her Christmas cards.

Mike Glazer