CONCENTRATION DEPENDENCE OF ATOMIC MEAN SQUARE DISPLACEMENT IN TITANIUM CARBONITRIDE TiCxNy

The work is dedicated to study of crystal lattice dynamics by means of the neutron diffraction method. The neutron diffraction method studies the dependence of the averaged root-mean-square displacement of atoms in titanium carbonitrides TiCxNy at various concentrations of nonmetals – carbon and nitrogen. Anomalous dependence of the averaged root-mean-square displacement of atoms in titanium carbonitrides TiCxNy on the relative total concentration of nonmetals (C + N) / Ti is established. With decrease of the general contents of nonmetals, that is, with the deviation of the alloy composition from stoichiometry, values of the thermal factor on the neutron diffraction pattern and the averaged root-mean-square atomic displacement at first decreases to the general concentration of nonmetals (C + N) / Ti ≈ 0.80. It increases with further deviation of the composition from stoichiometry. The nonmonotonic change of the root-mean-square atomic displacement with deviation from stoichiometry allows assuming that the dynamic distortion (thermal vibrations amplitude of atoms) in the lattice predominates over the static distortion, since otherwise the overall SCS should be only increase. This, apparently, testifies to difficult concentration dependence of the interatomic interaction in titanium carbonitrides, which has a heterodesmic character characterized by the presence ionic, covalent and metallic chemical bonds.

In addition, the work determines the averaged root-mean-square displacements and the individual root-meansquare displacement of atoms and the Debye temperature in stoichiometric titanium carbonitrides TiCxNy at different nonmetallic concentrations (C and N). They are practically equal at different ratios of the carbon and nitrogen atoms concentrations. The results can be useful for materials scientists and designers engaged in instrumentation and production free tungsten structural refractory materials to predict dynamic characteristics of titanium carbonitrides and manage these characteristics. 

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