Report of Visit to UK by Professor Martin Schoen
(TU Berlin)

7-11 May 1996

Martin arrived at Manchester from Berlin via Frankfurt on the morning of Tuesday 7 May. The journey was slightly jeopardized by the recent fire at Dusseldorf, which had made the originally scheduled route impossible; the revised connection at Frankfurt turned out to be very tight.

Martin mainly talked with Andrew Masters, his post-doc., Lena Akhmaskaya, and Julian Clarke from UMIST, with whom he shares many common simulation interests. He gave a seminar entitled Phase transitions in confined films. Computer simulations and theoretical results which covered shear-induced melting of confined solids, the microscopic structure of a near-critical fluid in a pore and some beautiful work on layering transitions in confined geometries. On Wednesday, Martin departed by train for London.

Martin arrived in London at about 5.30 p.m. on 8th May. We were able to find him accommodation in one of the Imperial College Guest rooms in Prince Consort Road just opposite the college. Ian Gould and David Nicholson took Martin to dinner at the Brasserie St Quentin in Knightsbridge, ensuing an auspicious start to his visit

We worked hard on the Thursday. Martin spent the first hour with Dominic Tildesley. They discussed Dominic's recent work on the calculation of the non-linear susceptibility and modelling of the second harmonic generation at the air/water interface and studies of flexible molecules dissolved in the Gay Berne fluid. Martin described his recent work on diffusion in confined monolayer films and a Taylor series Monte Carlo simulation method, which is reminiscent of the multiple time-step methods in molecular dynamics.

After coffee, Martin spent time with David Nicholson. David discussed his recent work on grand canonical simulations of mixtures in pores, his molecular dynamics studies of self-diffusion in slit geometries and new intermolecular potentials for zeolites. We introduced Martin to Dr Julian Gale, our Royal Society Research Fellow. Julian described his work based on the first density functional calculations of molecular adsorption on zeolite fragments. Recently this area has been extended to the use of plane-wave methods to study the binding of adsorbates in a periodic representation of a micro porous material.

We went to the Imperial College staff canteen for lunch and to take our mind off the food, we discussed the changes in Berlin since reunification. It is always a great pleasure to swap stories on the government's unusual approach to managing academic affairs. The chaos stretches across Europe.

In the afternoon Martin had an opportunity to meet the post-doc's and graduate students. He had an interesting session with Vladimir Sokhan discussing the adsorption of phenol at a water liquid/vapour interface and with Patrick Harvey on the penetration of oil into surfactant layers. Martin was full of ideas and questions and I think this session was enjoyed by all. We remembered to give him some time to think about his own talk and we had arranged tea for 4.00 pm in the old part of the Chemistry Building, which houses some magnificent Victorian lecture theatres.

We enjoyed an excellent seminar. Martin's observations on the significant changes in the lateral liquid structure of a fluid during pore filling gave rise to a large number of questions about the order and nature of the underlying phase transition. The seminar was much appreciated by a small but well-informed audience.

After a vote of thanks, we gave Martin a short seminar on the vagaries of the London Underground and delivered him with clear instructions for Paddington by way of South Kensington.

Martin arrived in Bristol shortly after 9 p.m., and had dinner with Mike Allen at Browns Restaurant, recently converted from the University Student Refectory into a place that serves decent food. An early start the next day saw Martin in detailed discussions with Mike and his students. Philip Camp described recent simulations of biaxial nematic ordering in rod-plate mixtures, and the mapping out of the isotropic-nematic coexistence line for uniaxial hard ellipsoids by Gibbs-Duhem integration. This work is directly connected with testing recent improvements to the classical Onsager theory. Julian Brown outlined work carried out in collaboration with the group in Seville, investigating the effect on the phase diagram of systematically varying parameters in the Gay-Berne model. Martin has recently begin work on the effects of confinement and simple models of molecule-surface interaction on this type of model, and there seems to be some scope for collaboration and exchange of information in the future. Mike Allen also described recent determinations of the Frank elastic constants for this system by his student Mark Warren. Martin spent some time discussing a range of simulations with Jeroen van Duijneveldt, a Ramsay Research Fellow in the group.

With Bob Evans, Martin discussed theoretical aspects of the effects of confinement on phase transitions, some of the related experimental work going on in the laboratory in the group of Ashraf Alam, and the effect of the long-range form of the pair potential on the asymptotic form of pair correlation functions and density profiles. With Bob, Mike Allen and Hector Dominguez, he discussed some simulation work of Hector's on the effect of confinement on the freezing transition, which involves some quite delicate free energy calculations.

The seminar was quite well attended, provoked much discussion, and was appreciated by all. Afterwards, Martin had the chance to talk to Margarita Rivera, a graduate student in the polymer group, who has performed a range of experiments on complex molecules adsorbed on surfaces using STM/AFM apparatus.

On Saturday, some time was devoted to tourism. Mike and Martin started by giving moral support to Philip Camp, who was playing in a two-day croquet tournament (more hard-particle dynamics). Then a guided tour of Bristol, part on foot, part by boat, followed. After lunch, Mike went home to watch the FA Cup Final on television, while Martin slept back at the University accommodation; it is debatable who had the more interesting time. A final dinner at the local Balti restaurant brought the visit to an end. Martin departed very early next morning for Heathrow by coach.

All those involved thought the visit worthwhile. Our thanks go to Martin Schoen for undertaking such a tour, talking to so many people, and being so interested in everything he encountered.

CCP5 would like to thank the institutions who cooperated in this venture.