MULTIWAVE MODULATION OF POLYDOMAIN CRYSTALS

Anatolii Ustinov¹, Lyudmila Olikhovska¹ and Ivan Shmyt'ko²

¹Institute for Metal Physics, 36, Vernadskii St., Kiev, 252142, Ukraine, ustinov@imp.kiev.ua

²Institute of Solid State Physics, Chernogolovka, Moscow district, 142432, Russia

Two displacement waves propagating along one crystallographic direction was experimentally shown [1, 2] to occur in SC(NH₂)₂ and TMA-ZnCl₄ crystals. Moreover, additional satellite peaks appeared in diffraction patterns alongside with satellites of base modulations. Those additional peaks can be considered as an evidence of correlation between base modulations.

Separation of a crystal in domains by antiphase boundaries should be taking into account while determining this crystal structure. So, diffraction data analysis should consider both possibility of correlation between displacement waves in a domain and possibility of modulation parameter correlations between domains as a result of their "interaction".

In the paper the results of simulation of X-ray scattering intensity distributions by polydomain crystal with one or two transverse waves of displacements (propagating along one crystallographic direction) are considered. Simulations were performed in the kinematic approach with Monte-Carlo method application. Influence of different "interaction" types both between waves within one domain and between domains was studied.

Peculiarities in X-ray diffuse scattering distribution were found out for certain of "interaction" types between domains modulated by one or two waves. These peculiarities allow to determine character of correlation with high degree of certainty. However, there are crystal models with a certain type of "interaction" between domains modulated by one wave of atom displacement which diffraction patterns are qualitatively similar to diffraction patterns for crystals with two modulation waves. Possibility of substructure characteristic determinations by quantitative of X-ray pattern analysis is justified for polydomain crystals modulated by several waves of displacement.

The work was supported by INTAS grant No 93-3230-ext.

[1] B.Sh.Bagautdinov, V.V.Gladkii, S.N.Kallaev at al., Pis'ma v ZhETF 59 (1994) 113- 117
[2] B.Sh.Bagautdinov and I.M.Shmyt'ko. Pis'ma v ZhETF 59 (1994) 171-174