by Igor GORYUNOV, journalist
In the article which follows we would like to introduce our readers to one of this country's unique centers of research-the RAS Institute of High-Pressure Physics named after Vereshchyagin (IFVD). Focusing on the fundamental and applied aspects of physics of highly compressed matter, the Center is unparalleled in this and other countries.
The experts tell us that practically all visible matter in the Universe is concentrated in vast self-gravitating bodies, like planets and stars. According to calculations, from 90 to 95 percent of this matter is under pressure of over 10 kbar. And in our studies of the matter one of the challenges is to try and understand how it behaves in these particular conditions.
The IFVD was founded back in 1958 in the town of Troitsk near Moscow on the basis of the Laboratory of Super-High Pressures of the USSR Academy of Sciences. The first director of the Center was Academician Leonid Vereshchyagin. His scientific interests were formed under the influence of the American researcher, Prof. Percy Bridgman (1882-1961), the founding father of high-pressure physics and a Nobel Prize laureate.
Originally conceived as a center of basic research, the Institute was given a very specific applied objective practically right from the start. By that time the Americans synthesized artificial diamond (1955) - a breakthrough which boosted the industrial potential in an appreciable way. And the Soviet experts in the field were instructed to match the American achievement within the shortest possible span of time. And, naturally enough, the task fell on the shoulders of the IFVD as the leader in high-pressure technologies.
The process of synthesis of diamonds was known from the mid-1930s when the celebrated Soviet scientist, Prof. O. Leipunsky, published his article in the Uspekhi Khimii (Achievements of Chemistry) journal in which he described his ideas. The task of translating them into practice was assumed by IFVD specialists under the leadership of Academician Vereshchyagin in 1960. And their efforts were crowned with success. One of the experts engaged on the project was Yuri Konyaev, Cand. Sc. (Tech.), who held the post of Assistant Director. He recalls that they found a simpler, more effective and reliable technique of producing synthetic diamonds than the method of compressing and heating of graphite suggested by the Americans. The discovery made it possible to launch the production of synthetic diamonds on an industrial scale not only in the Soviet Union, but also in other countries of the Socialist
Community. Advantages of the new method were demonstrated by the fact that by the early 1980s the volume of production in the Soviet Union was two times greater than that of the United States.
In the subsequent years the Institute was enlarged with the addition of new labs of a more applied nature which attended to the needs of industrial producers of synthetic diamonds and other superhard materials (such as diamond-like boron nitride which was also synthesized there for the first time). Institute experts also designed special appliances for the leveling out (by tilling) of rapidly wearing landing strips for strategic aircraft.
"WHAT'S IN MY NAME?"
The "diamond project" served to promote the Institute's wellbeing to a considerable extent with special subsidies being provided for the construction and development of what was called its experimental base. This included, for example, putting into operation in 1975 the world's most powerful research press with a capacity of 50 thousand tons.
But the IFVD status of a first-class research center was finally sealed in 1961 when its experts synthesized an overdense modification of silicon. That was an original project of fundamental nature which also offered the key to the understanding of the material composition of our planet. The project was carried out by the present Director of the Institute, RAS Corresponding Member (then a postgraduate) Sergei Stishov, and the head of a department (then junior researcher), Svetlana Popova, The former wrote a dissertation proving that the bulk of the Earth's matter consists of ordinary silicon which assumes a denser, or more compact state under high pressures. Later on specialists discovered in the Arizona meteorite crater a mineral which was a natural analogue of overdense silicon (the Americans called it "stishovite" in honor of its discoverer) produced in the laboratory conditions by Troitsk experts. As has now been established, the lower mantle of the earth and planets of the earth group consists of a material containing silica in the same "coordinates" (its closest atomic environment) as the "stishovite".
The synthesis of this overdense modification of silicon dioxide carried out by IFVD experts demonstrated the decisive role of phase transitions in the formation of the structure of the earth and the planets. This mapped out the road of geophysical studies for decades ahead. The discovery also initiated years of studies into the synthesis of what are called metastable phases of high pressure. In the year 2000 its experts grew up for the first time big monocrystals of "stishovite" in the conditions of high pressures and temperatures. Studies of the physical properties of this material promise rapid progress in our understanding of the processes occurring in the bowels of the earth and other heavenly bodies.
VITREOUS "HEART" OF THE EARTH
Studies of matter transformations in the conditions of high static pressure is one of the basic areas of research by IFVD scientists. These investigations rest on a solid fundamental base which makes it possible to model the "behavior" of matter in a condensed or supercondensed state.
- This makes it possible for our researchers, - says Deputy Director of the Institute, Dr. Vadim Brazhkin, to pose and solve some interesting geo-
physical problems. Their recent experiments shed light on certain aspects of the structure of the earth core. This was done in the following way.
Scientists investigated the crystallization of iron melt at rapid cooling and high pressures and established that under such conditions its viscosity increases by billions of times. And then they modelled processes occurring within the earth's core. Their preliminary conclusion is that the latter is not in crystalline, as was earlier believed, but in an amorphous vitreous state. That means that at pressures of the order of 3-4 Mbar, iron melt ceases to be fluid-stops flowing- and becomes vitrified. This offers a completely new view of the structure of the core of our planet: this turns out a viscous-elastic body with a constantly and gradually increasing viscosity of up to the vitreous values. The new theory is in good accord with the behavior of seismic waves on the border between the outer and inner zones of the earth's core. And in their frequency range this amorphous substance manifests itself just like a solid one. And if this is so, the temperature in the center of our planet has not yet sunk below the melting point. And that gives greater preference to the theory of a more vitrified, but not yet crystalline state of the core. That explains why it has been impossible until now to observe free oscillations of the inner core under the effect of the tidal pull of the Moon. Incidentally, rapid oscillations of the earth axis depend upon the absolute values of viscosity of the earth's interior.
What's more - the fact of the stable existence of high viscosity metals can cause a reappraisal of many models of the evolution and movement of matter within heavenly bodies and generation of their magnetic field: the mixture of hydrogen and helium, which the stars and giant planets are made of, assumes the form of liquid ultra-viscous metal when submitted to pressures of tens of millions of atmospheres.
Today IFVD researchers still do not loose sight of their favorite - the synthetic diamond. Quite recently they studied its "extreme" properties. It was established that its record value of volume elasticity module stems from its unique atomic density (number of atoms per unit of volume), and the effects of its covalency (bonds orientation) play no substantial role in this case. At the same time its specialists have synthesized and studied over the past few years new high- temperature superconductors on the basis of mercury compounds. They obtained samples with some record values of superfluidity (Tc=154K at pressure of 1.5 Gpa). This makes it possible to expect that new and superior materials for superconductors will be developed in the future.
Using new supersensitive methods for superconductivity assessments has made it possible for Institute researchers to identify and study it in a range of elementary substances at pressures of up to 2 Mbar. Thus at 1.6 Mbar for sulfur Tc amounted to 17 К.
IFVD scientists have been the first in the world to identify and study new types of phase transitions in "disordered" systems like fluids and glasses. They developed at the same time high-pressure Toroid apparatuses with what they called a "modified profile". Using a solid alloy developed here, it
can develop pressure of up to 16 Gpa in a volume of about 0.3 cm 3 which is a record for units of this type.
- Our researchers have always combined theoretical and applied studies. In recent years, however, the emphasis has been on fundamental physics - stressed Prof. Stishov. These changes reflect our present lack of funds. And fundamental studies are still being supported from the federal budget somehow. And, as different from the Soviet years, when our applied studies were lavishly financed by the military-industrial complex, no one needs them now. Today we can no longer engage on a full scale into low-temperature physics and physics of super-high pressures because such studies cost lots of money. The Institute practically cannot afford developing new high-pressure chambers with diamond anvils. We see a way out of this situation in the establishment of international cooperation-something which should be encouraged by the unique nature of our center. We are already engaged on many joint projects with our foreign colleagues, and our researchers, including young ones, often travel abroad.
Science, needless to say, is international in its essence, but in every country there is a particular approach to the solution of various particular problems. This can provide the basis for the birth of new schools of research. For example, in theoretical physics there can be many solutions of one and the same problem. In the United States and countries of Western Europe with their abundance of computer hardware preference is given to digital methods. As for us, Russians, our labs have always been plagued by computer deficits and this must have encouraged analytical approach. And even now when computers are readily available here many of our theoretical scholars choose to cling to the traditional ways.
And the same generally applies to our research instruments and equipment. The aforesaid Toroid high-pressure device features highly scattered pressure values in its working area, but is very simple to operate. Its American analogue Belt is more demanding, has considerable service costs but features a larger volume of the working chamber.
But the different approaches of the Russian and foreign scientists to dealing with various problems are not a barrier, but rather an invitation to closer mutually beneficial cooperation. And this determines to some extent the prospects of the Institute activities for the near future.
Our subjects of research - says Prof. S. Stishov, - mirror the plans of our researchers. In the opinion of the Institute management it is the scholarly interests of the staff which should guide the activities of the Center and research projects should not be ordered from above.
We do believe, however, that the level of our fundamental studies should be on a par with that of our foreign counterparts and that our applied science should be at least competitive on the domestic market. These objectives determine the strat-
egy of our researchers. We have a staff of 115, including 20 Doctors and 76 Candidates of Sciences. Some 50 of our staff are already "providing" first-rate science and another 20 are capable of producing "marketable commodities". The task of the management is to provide normal conditions for them all. The record of our achievements includes two discovery certificates and some 400 patents on inventions (including 48 foreign patents).
And, naturally enough, we give much attention to the training of our young staff. And this educational process is being conducted not according to textbooks, but from the teacher to the student. No better way has been invented so far and we have no problems with following these tactics. We are training young researchers who, in my view, will have a real future in science. Above all in the science of this country.
Today, continues Prof. Stishov, everyone speaks of the importance of modem science. But the society really becomes aware of its importance only when it encounters some really serious problems. And that applies not just to the Russians, but also to the Americans. And I say so not only from hearsay. For the past several years I have been working for several months a year at the Los Alamos National Laboratory. In the United States today what I would call decent financial backing is available only for biology and medicine. And politicians believe that if and when some firms require some innovative technologies, it is up to them to incur the expenses. But there can be no effective industrial production without fundamental science and the educational system will be degrading. The places of scientists in college chairs will be occupied by dilettantes, and people will start forgetting simple arithmetics. In the final run all of our science could boil down to astrology.
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