Scaling properties of the ν1 Raman active nitrate mode in doped ammonium and potassium nitrate crystals

• Published in: The Journal of chemical physics 1998-12, Vol.109 (23), p.10311-10315
• Main Authors: Li, Shuling, Ma, Shuguo, Wu, Guozhen
• Format: Article
• Language: English
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.477726

The Raman intensity behavior of the nitrate modes during phase transitions is analyzed via the power law |T−Tc|β for (F−, Cl−, Br−)-doped NH4NO3 and (Na+, Rb+, Cs+, Ag+)-doped KNO3 crystals. The exponent β is shown to be highly dependent on the degree of doping. This observation is based on the resonance behavior of the resident dopant. The spatial extent of the resonance mode is shown to be the characteristic dimension for the crystal domains during phase transition. This extent is demonstrated to be proportional to dc, the characteristic average distance between dopant ions at which β values of the nitrate ν1 and ν4 modes are the same. The scaling property as evidenced by β of the ν1 mode is analyzed via the (mass of the dopant)−1/2 scaled average distance between dopant ions which is an important parameter for characterizing the doping effect. Previous results for the (Na+, K+, Ag+, Pb2+)-doped NH4NO3 crystals are also employed to complete the analysis [S. Ma, G. Wu, and H. Wang, J. Chem. Phys. 108, 7758 (1998)].