First Order Phase Transformations: Scaling Relations for Grain Self-Correlation Functions

Abstract

At high pressure many alkali halides transform from the NaC1 (B1) structure to the CsCl (B2) structure. We have recently studied this transformation in polycrystalline RbI, which transforms at a critical pressure, P_c = 3.5 kbar.¹ By observing the time development of the neutron diffraction pattern after sudden increase of hydrostatic pressure from P<P_c to P>P_c we directly deduced X(t), the fraction of the sample converted from metastable to stable phase, as a function of time. We showed that X(t) taken at different P could be approximately scaled onto a universal growth curve by introducing an adjustable characteristic time τ(P) for each curve, such that

EquationSource% MathType!MTEF!2!1!+- % feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbWexLMBbXgBd9gzLbvyNv2CaeHbl7mZLdGeaGqiVu0Je9sqqr % pepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9vqaqpepm0xbba9pwe9Q8fs % 0-yqaqpepae9pg0FirpepeKkFr0xfr-xfr-xb9adbaqaaeGaciGaai % aabeqaamaabaabauaakeaacaWGybGaaiikaiaadshacaGGSaGaamiu % aiaacMcacaaMe8Uaeyypa0JaaGjbVlaadIhacaGGOaGaamiDaiaac+ % cacqaHepaDcaGGOaGaamiuaiaacMcacaGGPaGaaiOlaaaa!509B!]]</EquationSource><EquationSource Format="TEX"><![CDATA[$$X(t,P)\; = \;x(t/\tau (P)).$$

(1)

This is demonstrated in Fig. 1.