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Tributes to Victoria Buch
’ A PASSION FOR SCIENCE: MEMORIES OF VICTORIA BUCH FROM HER GRADUATE STUDENT YEARS AND THROUGH HER CAREER (BY R. BENNY GERBER)
I
got the impression that Victoria Buch had great potential for research from my first meeting with her in the Fall of 1977. She walked into my office at The Hebrew University of Jerusalem to inquire about joining my group as an M.Sc. student. By her file, she had an outstanding record as an undergraduate, having graduated with Excellence for the B.Sc. Her manner seemed to indicate a slightly absent-minded behavior, yet her thinking was sharp and focused. When discussing possible research topics, shy as Victoria was, her input was very incisive. Scientific discussions with Victoria, as many colleagues have commented years later, were always interesting and vibrant. Also, her scientific outlook was unusually broad for a young student. She refused, however, to commit herself beyond the M.Sc. degree, stressing that she needed to convince herself that she had the potential for continuing in research. Inversion of Rotationally Inelastic Scattering Cross Sections. I proposed, and Victoria accepted, a topic in scattering theory. r 2011 American Chemical Society
Around that time, the first differential cross sections for atommolecule scattering were being measured. The challenge was to find a direct way for obtaining the interaction potential, and especially the anisotropic part of the potential from the measured elastic and inelastic cross sections. In the work that Victoria and I did, this was accomplished using semiclassical scattering theory. With the method at hand, we formed a cooperation with Professor Udo Buck, a pioneer in this field at the Max-Planck Institute in G€ottingen, Germany. This led to two publications, one in Phys. Rev. Lett.,1 the other in J. Chem. Phys.,2 the first papers of Victoria’s career. Victoria demonstrated abilities in deriving approximations, and equally important, it became obvious that she excelled in doing theory in close cooperation with experimentalists. These remained great points of strength of Victoria’s work throughout her career. Most important, with two good publications, and with a grade of Excellence for her M.Sc. research, Victoria was confident that she should carry on for the Ph.D. Quantum Dynamics of Polyatomic Vibrations and the Time-Dependent Self-Consistent Field (TDSCF) Approximation. For her doctorate, Victoria Buch chose to explore vibrational states of polyatomic systems, including both stationary states and dynamics in time. She was one of the most prolific and creative students I have had, and in addition, work with her was also especially stimulating because of her independent, critical thinking, the lively, invigorating way of discussing ideas, and the enthusiasm she brought to her research. I had a small, but truly outstanding group at that time. Victoria’s contemporaries in the group included in the beginning Max Berkowitz (now professor at the University of North Carolina), Tamar Yinnon, and later Ron Elber (now professor at the University of Texas at Austin). Victoria interacted very well with the other members in the group, showed interest in their topics, and was characteristically involved in vigorous discussions. She worked very hard, often staying very late hours in the Laboratory. As the cleaning ladies told me, she would in cases collapse on a sofa in the small library/ meeting room of The Fritz Haber Center and be awakened next morning by the cleaners. During the early phase of her doctorate, Victoria would occasionally disappear for periods of a few days. Recently, after Victoria had passed away, Tamar Yinnon told me the secret behind this: Victoria wanted to solve by herself the problems she faced in her research, and not to be advised by me what to do. Such was her quest for independence! The highlight period of Victoria’s doctorate was in 1981/2. I went to Northwestern University on sabbatical leave and arranged for Victoria to join me for several months. With her special gifts for scientific discussions and interactions, Victoria contributed greatly to successful collaboration projects with Mark Ratner and with George Schatz. We pursued then a new approximate quantum mechanical approach for the vibrational Special Issue: Victoria Buch Memorial Published: June 09, 2011 5709
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The Journal of Physical Chemistry A dynamics of polyatomic systems. The idea was to adapt the time-dependent self-consistent field (TDSCF) approximation, proposed by Dirac in the early years of quantum mechanics, for the new context of quantum molecular dynamics. The early applications we pursued were to dissociation dynamics of van der Waals clusters. The first paper on the TDSCF approximation that I coauthored with Victoria and with Mark Ratner seemed to have had substantial impact.3 The paper stimulated or influenced work by other groups on quantum vibrational dynamics of polyatomic systems. In particular, dynamical mean-field methods and other extensions have proved of interest over the years. The applications to processes in van der Waals clusters made a contribution to the understanding of vibrational predissociation dynamics of these systems. A second paper, applying TDSCF to vibrational predissociation of four atomic clusters of the type of I2NeHe, in cooperation with George Schatz and Mark Ratner,4 was also well received in the field. These papers were Victoria’s strongest contributions from her doctorate, although she wrote a number of other nice papers, in particular on energy spacing and intensity distributions of highly excited vibrations of model polyatomics. With these fine research accomplishments, Victoria Buch wrote up her thesis and was awarded the Ph.D. (in 1984). She also received for her achievements in research a prestigious Weizmann Fellowship for pursuing postdoctoral studies abroad. Postdoc at the Harvard-Smithsonian Center for Astrophysics. Victoria became a Postdoctoral Fellow in the group of Prof. A. Dalgarno at the Harvard-Smithsonian Center for Astrophysics. She went for the postdoctoral position with Ron Elber, her husband at the time, and with their baby daughter Dassi. (Ron accepted a postdoctoral position with Prof. Martin Karplus at the Chemistry Department.) With her typical enthusiasm and dedication, Victoria had totally immersed herself in the study of her new field— astrochemistry. I heard from several experts that Victoria developed an extensive knowledge of a range of areas in astrophysics. Years later, she gave several public lectures in this field, and these were exciting, and well-received. Victoria’s main topic of research in the Dalgarno group was on trapping and recombination of hydrogen atoms on interstellar grains, a subject on which she published several papers. An important influence of Victoria’s postdoctoral field on her subsequent career was what she learned on ices and on hydrogen clusters, topics on which she did outstanding research some years later. On the Faculty of The University of Illinois at Chicago. After two years as postdoc, Victoria applied for faculty positions in the U.S.A. She accepted in 1987 an offer of Assistant Professorship at UIC, as did her then husband, Ron Elber. In her first years at UIC, Victoria’s research focused mostly on sticking, absorption, and spectroscopy of atoms and molecules on surfaces. She cooperated during that time with Michael Trenary, who did IR experiments on chemisorbed species on Pt surfaces. However, her interests drifted increasingly toward ices, adsorbates on ices, and in close connection with this also toward the interactions between H2O and molecular species. This direction proved very fruitful for Victoria, and very soon she obtained significant results in this area. Victoria was able to adapt, apply, and develop methods and computational tools for addressing very different aspects of the problem. This approach on several fronts of the field included ab initio calculations on the molecular interactions involved, molecular dynamics simulations on formation of condensates, and computational vibrational spectroscopy for analyzing adsorbate sites. At this time, around 1990, Victoria Buch also began several collaborations that were to last for years and that greatly advanced the field. She began to
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collaborate with Paul Devlin, especially on the spectra of ice particles and of adsorbates on these particles. She also began a very fruitful cooperation with M. Szczeniak on ab initio calculations of complexes of water. One of the most influential papers of Victoria Buch in that period, coauthored with her student O. Zhang, is on the formation dynamics and structural properties of amorphous ice condensates.5 This paper, and related contributions around the same time, provide interesting insights into growth mechanisms of amorphous ices. Victoria Buch had gifts for developing simple models and approximation methods. As of this stage in her career, she also developed the ability to powerfully use large-scale simulations. She had the dedication and depth for extracting insights from the complexity of the computations. She became exceedingly good at using such tools. Victoria’s research at UIC was developing with great momentum at this stage. She got tenure and was promoted to Associate Professor in 1992. However, she decided to return to Israel and accepted a position of Senior Lecturer at The Hebrew University of Jerusalem, the place where she began her career in chemistry. On the Faculty of The Hebrew University of Jerusalem. I was very excited when Victoria Buch decided to accept an offer from The Hebrew University, to take up a position here, as of October 1992. Not only was I sure that she would do outstanding research herself, but also I expected from knowing her that she would be a stimulating force, a source of ideas and directions that could influence all of us. Viki’s untimely death does not change the fact that these expectations were more than fulfilled. Victoria’s years at The Hebrew University were a golden age in her research career, and a great gift to theoretical chemistry here. First, a note on Victoria as a teacher: Her performance as classroom lecturer was not always equal, but frequently she taught inspiring courses, for which the students expressed enthusiasm. She often injected interesting, thought-provoking ideas and perspectives into her undergraduate courses. Her research flourished, and I think she made her most important contributions here. As at UIC, Victoria always had a small group, no more than 23 students and postdocs most of the time. However, for these few students and postdocs, she was a superb mentor, who brought out their best research skills. Victoria did not just direct young co-workers, but pursued research with them by way of participation. Thus, Victoria always did “hands on” research also in seemingly technical activities: code writing and debugging, or looking in painstaking detail at complex simulations, to extract insights. Victoria developed an impressive network of long-term collaborators and co-workers. The beginning of this framework of collaborators was already noticeable during Victoria’s years at UIC, but it increased greatly during her career at The Hebrew University. Victoria’s long-term collaborators were part of her most important and creative contributions. Several of those were experimentalists: with J. P. Devlin (Oklahoma State); with U. Buck (Max-Planck Institute, Goettingen), she obtained seminal results on water clusters, she made pioneering contributions to ice surfaces and to adsorbates on ices. Other important experimental-theoretical cooperations, toward the end of Victoria’s life, were with M. J. Shultz (Tuffts) and G. L. Richmond (Oregon). Victoria also had very fruitful long-term cooperation with several theoretical and computational groups: J. Sadlej (Warsaw); M. Parrinello (ETH, Lugano); P. Jungwirth (Prague); A. Milet (Grenoble); N. UrasAytemiz (Isparta, Turkey); A. D. Hammerich (UIC); M. Pincu (UC, Irvine); F. Mohamed (Humboldt U., Berlin). Victoria was able to bring to bear on the problems she pursued a range of 5710
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The Journal of Physical Chemistry A diverse methods and techniques: approximations and algorithms she herself had developed, or tools she learned from others, e.g., CP2K from the Parrinello group, or standard techniques, such as ab initio codes she judged suitable for the systems at hand. Consideration of available experimental data, for which she had great insights, was also an essential part of the list. Most of Victoria’s contributions from this period of her career will be described by other coauthors of this biography. Here, I will briefly discuss just several highlights of this superbly creative research period. Rigid-Body Treatment of Molecules in Diffusion Quantum Monte Carlo (DQMC) Simulations. Application of the DQMC method to weakly bound complexes and clusters, e.g., (H2O)n, (H2)n, poses major difficulties since the energy scale of the intramolecular interactions differs greatly from that of the weak intermolecular forces. This makes it impossible to achieve good accuracy of the intermolecular vibrations when all degrees of freedom are included in the Monte Carlo process. Victoria was able to overcome the difficulty, by developing an algorithm in which the intramolecular vibrations of the monomers in the cluster are treated as rigid.6 This very elegant approach, originally demonstrated for H2OH2(para) and H2(ortho) complexes found many fruitful applications by Victoria in cooperation with J. P. Devlin and with U. Buck, and with other groups. It motivated other important developments in DQMC by A. B. McCoy (Ohio State), K. B. Whaley (Berkely), and several other researchers. I view this as one of Victoria’s finest and most important contributions. Quantum Path-Integral Simulations of Mixed Para D2 and Ortho D2 Clusters. To treat temperature effects on the quantum clusters D2(para) and D2(ortho), and in particular to explore the role of molecular orientation effects on para/ortho mixtures, Victoria developed and applied a variant of Feynman pathintegral simulations.7 In addition to the very interesting algorithm, the paper predicts fascinating effects of temperature on “segregation” versus “solvation” of ortho and para species in the mixed clusters. Also this paper has a good following in the research community. Structure and Spectra of Water Clusters of Moderate Sizes. Victoria Buch made seminal contributions to the spectroscopy of water clusters. The work on clusters of moderate sizes (n e 10; roughly) can be said to provide detailed information on the 3D structure of the species. This work was done in collaboration with U. Buck (Goettingen)8 whose innovative experiments made possible studies on size-selected clusters (or to narrowly dispersed size distributions). Great insight into the structures, and into order and disorder, of these systems has emerged from this powerful theoreticalexperimental cooperation.8 This work continues to have a very major impact. At the same time, in cooperation with J. P. Devlin, Victoria Buch made also contributions to the understanding of structural properties of large ice clusters, analyzed through infrared spectra.9 These two types of systems provide a conceptually important link between small ice clusters and macroscopic ice particles. Other very important collaborative researches of Victoria Buch in this period will be described in the sections of other coauthors of this scientific biography. Research When Facing Mortal Illness: Cooperation with Victoria during Her Final Days. Victoria was diagnosed with cancer approximately a year and a half before this illness took her life. There was never too much ground for optimism. Victoria
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continued, however, to work with dedication and enthusiasm until the very end, and kept doing high quality, edge-cutting research. She did her utmost in her research projects, as matters deteriorated, as she underwent difficult treatments, appalling pain, loss of mobility, and sedation. During the last year of her life, her group was larger than usual and very active. It included Dr. Lukasz Cwiklik and Dr. Barbara Jagoda-Cwiklik, as postdocs (both now in Prague), as well as the personal friends and research visitors: Dr. Madelein Pincu (now at UCI) and Dr. Audrey Hammerich. During this time and until the very end, Victoria led the projects and participated very actively. Shortly before Victoria was diagnosed with cancer, we began to plan a new collaborative project aimed at studying the interactions of saccharides with water and with ions, and the structural consequences and the spectroscopic signatures thereof. I submitted a proposal to DOE on this topic, indicating planned cooperation with Victoria Buch and with Prof. J. P. Simons (Oxford). At the time, when the proposal was written, Victoria suffered already serious consequences of her illness. Nevertheless, she provided me with great help for the preparation of the proposal: objectives, ideas, and considerations on relevant methods. In the meantime, Dr. M. Pincu, a long-time friend of Victoria’s, arrived as Visiting Researcher at The Hebrew University, to pursue this topic. Already in a difficult condition, Victoria worked closely and intensely with Madeleine, and rapid progress was made. She continued with her typical enthusiasm for research and bubbled with ideas. She was delighted when I told her that DOE decided to fund the project. The last time I saw Victoria was just before she died. She was confined to her home in hospice conditions and had to be sedated most of the day. She directed our discussions strictly to research, which was clearly very much on her mind. Victoria’s comments were, as always, incisive, sharp, and helpful. She addressed points of the algorithms in detail, although she was visibly in great physical discomfort. She urged me to finish and publish a first paper on the results, as soon as possible. We submitted the paper, with Victoria as coauthor, several months after her death. The paper deals with structure and dynamics of sugarwatersalt complexes.10 Research was to Victoria a great mission, a major priority in life. It was a great privilege for me to work and interact with her.
’ REMEMBRANCE OF TWENTY YEARS OF RESEARCH COLLABORATION WITH VICTORIA BUCH—1989 TO 2009 (BY J. PAUL DEVLIN) I became familiar with Victoria’s research program in 1988 through a request from J. Chem. Phys. to review a short paper on the simulation of the growth and structure of a large cluster of amorphous ice (ASW).11 It reported a novel study that happened to match in time my groups first efforts to characterize spectroscopically the surface of amorphous ice films and the interaction of weak adsorbates with the surface groups. Victoria quickly managed to show that an observed infrared doublet for the dangling OH groups reflected a difference between 2- and 3-coordinated surface water molecules.12 With that satisfying result, we were encouraged to attack problems presented by weakly adsorbed molecules including H2, N2, and CO. The adsorbed H2 data proved to be most intriguing as the H2 stretchmode infrared band that first formed near 12 K shifted over a period of hours to a new higher frequency position. Realization that this was an ortho-to-para conversion on the cold ASW 5711
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The Journal of Physical Chemistry A surface came slowly, requiring a detailed molecular dynamics study to confirm and extend the analysis.13 The latter included a nice fit of both the ortho and para rotational Raman spectra using the path-integral Monte Carlo technique.14 Eighteen years later the behavior of H2 on ice has received considerable attention with conclusions that seem to have deviated little from Victoria’s original insights. After George Ewing, with Terry Gough’s help, showed in the early 1990s the way to generate molecular nanocrystals with ease in a cold condensation cell, our interest switched to the nature of the surface of crystalline ice particles and the interaction of adsorbates with that surface. Victoria’s molecular dynamics simulations soon revealed important surface characteristics of the nanocrystals; i.e., the surface is disordered, the disorder is largely produced by a reduction in the density of high energy surface groups through formation of “distorted” hydrogen bonds between dangling-oxygen and dangling-hydrogen sites, and the reduced population, relative to an ordered ice surface, significantly decreases the surface reactivity.15 This reduction in high energy dangling groups, which is important in understanding the interaction with “reactive” adsorbates like HCl, also allowed an interpretation of the impact of intermediate-level adsorbates such as SO2, HCN, NH3, and H2S. Such adsorbates at submonolayer coverage influence the iceparticle structure as revealed by a 510% increase in the amount of ordered core ice. From the simulations it was clear that this increase can be attributed to adsorbate insertion into the distorted hydrogen bonds formed during surface reconstruction. This dereconstruction of the surface moves the structure toward that of an ordered ice surface and increases the interior order as well.16 At the time, Toennies’ group was providing evidence that the surface of a thin ice film on platinum was “oxygen ordered”, a result that seemed contradictory to the particle interpretations. Victoria ultimately concluded that the disorder from reconstruction is largely limited to quite small nanocrystals that have a significant surface curvature and is diminished by an increase of faceted surfaces with particle size (thinking that was a partial basis for her more recent research with Professor E. Tosatti17). The interaction of strong acids, and in particular HCl, with the surface of ice was of considerable research interest through the decade of the 1990s partially because of a catalytic role in ozonehole formation. So we acted to extend knowledge of the iceadsorbate systems to HCl. Data from our lab and that of Heon Kang indicated that below 80 K and with low HCl surface populations, molecular but distorted forms of HCl dominate. This suited the MD methods of the time, allowing Victoria to thoroughly examine the low-temperature distorted molecular states of HCl (and ammonia) on ice, with results consistent with experiment.18,19 Subsequent experimental results, by other groups studying HCl adsorbed on ice films on smooth metal surfaces, suggest that the molecular form of HCl is rare, even at 0 K. This does not contradict the earlier results, as there is ∼50% greater density of the solvating dangling groups at the surface of an ordered ice film. Victoria’s simulations particularly emphasized the importance of self-solvation to ionization showing that HCl donates a proton to the chloride of a second HCl with nearly the same efficiency as does a water molecule.19 As a result, selfinduced ionization is dominant for HCl coverage beyond 30% at 60 K, and for all cases above ∼100 K. More recently, after gaining experience with on-the-fly molecular dynamics in the lab of Prof. M. Parrinello, Victoria showed that states resembling those for HCl on an ice particle surface can be fluxional in nature moving
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on a picosecond time scale from one distorted state to another, including ionized states, through structural fluctuations that accompany low-frequency molecular motions.20 The study of ice surface reactivity toward strong adsorbates (including the barrier to release of protons to the ice interior21,29) led to a special interest in the series of ionic acid hydrates of HCl and the clathrate hydrates of small ether molecules. Nanocrystals of ice at >130 K were observed to convert rather quickly to acidhydrate nanocrystals, with the particular hydrate formed determined by the temperature and extent of exposure to the acid. The reaction in the presence of an abundance of acid was shown to follow a shrinking-core model, implying that the rate of conversion to the hydrate was controlled by acid diffusion through the crust of hydrate product. This focused Victoria’s interest on the mechanism by which the acid (or in a more recent study a potential clathrate-guest molecule24) moves through the hydrate crust to the reaction interface. The combination of simulations with experiment led to the tentative suggestion that the diffusion mechanism involved molecular HCl. The acidhydrate computations were largely within the Parrinello group, including a detailed study of the fascinating structure of the crystalline monohydrate of HCl.22 Eventually, each of the HCl hydrate structures and spectra was simulated, demonstrating the breadth of condensed-phase behavior of protons with properties ranging from that of an Eigen ion in the hexahydrate to a Zundel ion in the tri- and dihydrates to a chloride solvated H3Oþ in the monohydrate.23 Spectroscopically perhaps the most interesting conclusion was that proton sharing in the acid hydrates typically fluctuates with low-frequency modes, giving rise to quite broad bands structured by Fano antiresonances with narrow molecular states (i.e., Evans Holes). It is not a stretch to say that Victoria died while working on the problem of how small molecules diffuse rapidly through clathrate hydrates of H-bonding guests even at temperatures as low as 110 K. She tentatively concluded that the result of Trout, that guest molecules of more common clathrate hydrates diffuse at much higher temperatures through holes in the ice-like lattice associated with vacancy defects, was only half of the picture for H-bonding guests. She identified the function of the H-bonding guests with stabilization of the otherwise high-energy vacancy defects through bonding with the dangling hydrogen and oxygen that they present.24 This BuchTrout mechanism represents the current best explanation of the catalytic effect of H-bonding molecules on the growth and transformations of clathrate hydrates.
’ THE LAST SABBATICAL OF VICTORIA BUCH (BY PAVEL JUNGWIRTH) First time we ran into each other was in the dark corridors of the Physical Chemistry building at the Hebrew University of Jerusalem in 1994. Victoria returned recently from the U.S. and was establishing her group in Jerusalem and I was just starting my postdoc with her former Ph.D. advisor Benny Gerber. So, we were both quite busy; nevertheless this was the period when we started an ongoing scientific dialogue, which eventually grew into a most inspiring collaboration. We kept in regular touch after I left Jerusalem but it was not before my sabbatical at the same place in 2001 that we started to work on a scientific project together. Since then, we visited each other frequently, talked together at conferences (most notably at the Telluride workshops that Victoria organized), and our collaboration culminated 5712
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The Journal of Physical Chemistry A during her sabbatical stay in Prague in winter/spring 2007. Let me briefly recall here three projects where I had the honor and pleasure to collaborate with Victoria, the latter two of which materialized during this memorable sabbatical. Possible Molecular Mechanism of Thundercloud Electrification. Around the turn of the millennium Victoria became deeply interested in atmospheric implications of cloud processes involving ice particles, of which she gained a detailed knowledge with her experimental colleagues Paul Devlin and Udo Buck. A process that we both found fascinating and yet not fully understood at the molecular level was the mechanism of atmospheric electrification during collisions between ascending ice crystals and falling graupels in maturing thunderclouds. The intriguing question was: What are the physical carriers of the transferred electric charge—water ions (hydronium and hydroxide), salt ions, or electrons? After a preliminary study25 where we convinced ourselves that we were capable of simulating collisions of aqueous particles, we realized that we needed to understand the dynamics of thunderclouds better to make a meaningful contribution. Victoria commissioned help from her colleague in the Earth Sciences Institute, Daniel Rosenfeld, who was very instrumental in enlightening us about the meso- and macroscopic picture of thundercloud electrification. This allowed us to propose and test by molecular dynamics simulations an atomistic model, which provided an explanation of polarity reversal in thunderclouds upon changes in aerosol loading.26 Indeed, events like forest fires or massive biomass burning can trigger vigorous storms where clouds have positive charge at the bottom and negative charge at the top, which is opposite to the usual situation. With Victoria and Daniel we drew a connection between salt containing aerosols from forest fires and the cloud polarity reversal. The first microscopic rationalization of this phenomenon using collisional transfer of different salt ions from the graupel surface to ice crystals caught the attention of atmospheric scientists and it was even featured in popular science literature; an article presenting our model entitled Spannung liegt in der Luft (The voltage is in the air) appeared in German Bild der Wissenschaft in 2007. It is, however, fair to say that most of the atmospheric community continues to understand thundercloud polarity reversal primarily in terms of changes in meteorological conditions, largely disregarding the underlying molecular mechanisms. Ice Nucleation in Pure and Salty Water. The golden age of collaboration with Victoria was her last sabbatical in 20067, a good part of which she spent with my group in Prague. One of her colleagues she brought with her for a few days was Sigurd Bauerecker from Braunschweig, Germany. With Victoria, we had visited Sigurd’s lab before and were captivated by his ultrasound levitation chamber that allowed for monitoring ice nucleation in freely suspended droplets using fast optical and IR cameras. Victoria, with her dry sense of humor told me: “This is fascinating —let’s put Sigurd into good use.” With Victoria and my former excellent student Lubos Vrbka on the computational side and Sigurd on the experimental one, we then managed to provide a consistent and complementary view on ice nucleation and freezing in pure and salty water.27 Our molecular dynamics simulations showed at a molecular level how an ice nucleus forms spontaneously in supercooled water and how salt ions get expelled to the periphery of the system. Sigurd’s fast cameras allowed him to monitor the same process on a more macroscopic size and time scale, following the progression of the ice front and release of latent heat. These were more than just graphically
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appealing pictures and movies (“seeing is believing”), providing hints to the detailed molecular mechanisms of ice nucleation and brine rejection. Autoionization at the Surface of Neat Water. Victoria arrived in Prague on New Year’s Day of 2007 after a stay in Parrinello’s group in Lugano, Switzerland. From there she brought not only the knowledge of the ab initio molecular dynamics technique but also contacts with that community, several members of which showed up in Prague, too. In particular, it was the visit of Anne Milet from Grenoble during which we started with Victoria our last collaborative project. The idea was to combine her and Anne’s expertise in ab initio molecular dynamics of water clusters and our experience with classical molecular dynamics simulations of ions at aqueous surfaces to address the interfacial behavior of the two inherent water ions— hydronium and hydroxide. Previous calculations by the groups of David Oxtoby, Liem Dang, and Gregory Voth and by ourselves pointed to a very interesting surface behavior of hydronium and now we wanted to address both of these ions at the same time. In the resulting two papers we sketched with Victoria, together with Paul Devlin (who also came to Prague), Anne Milet, and my outstanding student at that time Robert Vacha a picture of the water surface mildly enriched in hydronium and weakly depleted in hydroxide.28,29 These results not only caught some general attention (e.g., a couple articles in Chemical and Engineering News and one in Chemistry World) but also stirred quite a bit of controversy. After several years of intense computational and experimental research in numerous laboratories the smoke over water surfaces may now start to clear up and it is sad that Victoria is not here to see it. Let me end by sharing a lighter, nonscientific story from Victoria’s last sabbatical which, I believe, nevertheless characterizes some aspects of her approach to science. In February 2007 Victoria joined us for a week of skiing in the Orlicke mountains in northern Bohemia. We are a family of skiing addicts, so my idea was that I will serve as Victoria’s personal coach, passing part of the white powder addiction to her. Well, we got the skies, we got to the slope, I started my “training program” ... and it was a disaster. I did not quite realize that the last time Victoria skied was before she left Poland in 1968 and progress was thus slower than I expected. Be a professional, I said to myself, and with infinite patience and buckets of good spirit, I continued the skiing lesson. Until Victoria turned to me with the piercing, all-knowing look she gave me several times before, when I was running on her nerves, and said, quite colorfully, “Hey Pavel, I can do this myself.” So by the end of the week Victoria taught herself to turn elegantly and stop decently. Victoria, I will miss your lessons on stubbornness in the best meaning of the word. And most of all, I will miss your piercing look.
’ REFERENCES (1) Gerber, R. B.; Buch, V.; Buck, U.; Maneke, G.; Schleusener, J. Phys. Rev. Lett. 1980, 44, 1397. (2) Gerber, R. B.; Buch, V.; Buck, U. J. Chem. Phys. 1980, 72, 3596. (3) Gerber, R. B.; Buch, V.; Ratner, M. A. J. Chem. Phys. 1982, 77, 3022. (4) Schatz, G. C.; Buch, V.; Ratner, M. A.; Gerber, R. B. J. Chem. Phys. 1983, 79, 1808. (5) Zhang, Q.; Buch, V. J. Chem. Phys. 1990, 92, 5004. (6) Buch, V. J. Chem. Phys. 1990, 97, 726. (7) Buch, V. J. Chem. Phys. 1994, 100, 7610. (8) Buck, U.; Ettischer, I.; Meltzer, M.; Buch, V.; Sadlej, J. Phys. Rev. Lett. 1998, 80, 2578. 5713
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(9) Devlin, J. P.; Joyce, P.; Buch, V. J. Chem. Phys. A 2000, 104, 1974. (10) Pincu, M.; Brauer, B.; Gerber, R. B.; Buch, V. Phys. Chem. Chem. Phys. 2010, 12, 3550. (11) Zhang, Q.; Buch, V. J. Chem. Phys. 1990, 92, 15123. (12) Buch, V.; Devlin, J. P. J. Chem. Phys. 1991, 94, 4091. (13) Hixson, H. G.; Wojcik, M. J.; Devlin, M. S.; Devlin, J. P.; Buch, V. J. Chem. Phys. 1992, 97, 753. (14) Buch, V.; Silva, S. C.; Devlin, J. P. J. Chem. Phys. 1993, 99, 2265. (15) Devlin, J. P.; Buch, V. J. Phys. Chem. 1995, 99, 16534. (16) Delzeit, L.; Devlin, J. P.; Buch, V. J. Chem. Phys. 1997, 107, 3726. (17) Buch, V.; Groenzin, H.; Li, I.; Shultz, M. H.; Tosatti, E. Proc. Natl. Acad. Sci. U. S. A. 2008, 105, 5969. (18) Devlin, J. P.; Uras, N.; Sadlej, J.; Buch, V. Nature 2002, 417, 2691. (19) Buch, V.; Sadlej, J; Uras, N.; Devlin, J. P. J. Phys. Chem. A 2002, 106, 9374. (20) Devlin, J. P.; Farnik, M.; Suhm, M. A.; Buch, V. J. Phys. Chem. A 2005, 109, 955. (21) Devlin, J. P.; Buch, V. J. Chem. Phys. 2007, 127, 91101. (22) Buch, V.; Mohamed, F.; Parrinello, M.; Devlin, J. P. J. Chem. Phys. 2007, 126, 21102 and 74503. (23) Buch, V.; Dubrovskiy, A.; Mohamed, F.; Parrinello, M.; Sadlej, J.; Hammerich, A. D.; Devlin, J. P. J. Phys. Chem. A 2008, 112, 2144. (24) Buch, V.; Devlin, J. P.; Monreal, I. A.; Jagoda-Cwiklik, B.; Aytemiz-Uras, N.; Cwiklik, L. Phys. Chem. Chem. Phys. 2009, 11, 10245–10265. (25) Jungwirth, P.; Buch, V. Collect. Czech. Chem. Commun. 2003, 68, 2283. (26) Jungwirth, P.; Rosenfeld, D.; Buch, V. Atmos. Res. 2005, 76, 190. (27) Bauerecker, S.; Ulbig, P.; Buch, V.; Vrbka, L.; Jungwirth, P. J. Phys. Chem. C 2008, 112, 7631. (28) Buch, V.; Milet, A.; Vacha, R.; Jungwirth, P.; Devlin, J. P. Proc. Nat. Acad. Sci. U. S. A. 2007, 104, 7342. (29) Vacha, R.; Buch, V.; Milet, A.; Devlin, J. P.; Jungwirth, P. Phys. Chem. Chem. Phys. 2007, 9, 4736.
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