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Scientists are using computer simulations to predict material with a melting point of a record
Material scientists at Brown University (Rhode Island, United States) при using computer simulation calculated , that material made of hafnium oxide and carbon is the highest melting point of all known to date. In his calculations scientists have used the laws of quantum mechanics.
Metal hafnium was It opened at the beginning of the 20th century. It is itself a refractory - its melting temperature is 2506 K. Although it is smaller than, say, the famous tungsten (3695 K), but alloys with carbon and hafnium has long put records on the melting point.
For example, since 1930, a record for this indicator kept the карбид tantalum, hafnium (Ta 4 sub> HfC 5 sub>) - 4215 K. But the new material is a hypothetical wins in this competition with a minimum temperature of 4400 K. This is more than 3 / 4, the effective temperature of the surface of the Sun (5778 K). However, all this is only a theory - it is necessary to make the material more and test it in a very, very hot oven.
But the fact that such theories can count on a computer - it's a big step forward. "The advantage of the approach, which studies begin with computer simulations, is that we can test many different combinations without the high cost of the tests at once and find those options, which is to experiment in the laboratory, - explains Axel van de Vail, Assistant professor and co-author of the article. - Under normal circumstances, we would act at random - but now we know what we can experiment ».
With the help of a supercomputer the National Science Foundation, scientists simulate physical processes at the atomic level, simulating the behavior of hundreds of atoms, using the laws of quantum physics. Based on the structure of tantalum carbide, hafnium, scientists using the computing found what factors lead to such a high melting point.
It was found that tantalum hafnium carbide combines high specific heat of fusion with a small difference in entropy between the liquid and solid phases. Explains van de Vale, in the melting of the material increases its entropy, and if the difference between the entropy of solid and liquid states is small, the temperature required for the phase transition, such a material is quite high. On this basis, it was possible to select the material whose difference in entropy is lower than the original, and the melting temperature, respectively, above.
Because tantalum and hafnium alloys do rocketry parts (nozzle, gas rudders) and electrodes for air plasma and oxygen-flame cutting. Characteristics theoretically predicted material yet to be clarified in practice - such properties as mechanical properties, oxidation, etc., are important not less than the melting point. But, as noted, van de Vail, work on the theoretical calculation of the melting point - itself a landmark, since it is rather difficult to calculate, in comparison with the other characteristics of the materials.
Source: geektimes.ru/post/259520/
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