科研之友
微信
新浪微博
Facebook
分享链接
摘要
We have measured the linear dielectric susceptibility of two molecular glass formers close to T-g in order to estimate the size of the dynamically correlated clusters of molecules which are expected to govern the physics of glass formation. This size has been shown to be related to the dynamic dielectric susceptibility d epsilon(omega)/dT (epsilon: dielectric susceptibility, T: temperature, omega: frequency). To allow for an accurate determination of the T derivative, we scanned the interval 192 K < T < 232 K every 1 K for glycerol and 159 K < T < 179 K every 0.5 K for propylene carbonate. The resolution on T variations was about 1 mK. The result for glycerol is that the number of correlated molecules increases by a factor of 3 when T goes from 226 to 195 K. It has been shown that the non-linear susceptibility provides a direct measurement of dynamic correlations. To measure it, we used a standard lock-in technique yielding the third harmonic of the current flowing out of a capacitor. We obtained only an upper limit on the ratio of the third to the first harmonic, due to the non-linear response of standard electronics.
- 出版日期2007-5-23
- 单位中国地震局
