Gromnitskaya Elena L, Danilov Igor V, Brazhkin Vadim V
Institute for High Pressure Physics, Russian Academy of Sciences, Troitsk, Moscow 108840, Russia.
Phys Chem Chem Phys. 2021 Jan 28;23(3):2349-2354. doi: 10.1039/d0cp04550k.
We present a comparative ultrasonic study of the elastic properties of adamantane and 1-chloroadamantane at high pressure (up to 1.4 GPa) and different temperatures (77-293 K) and at order-disorder transitions. The ultrasonic method provides complementary pictures of the order-disorder transitions in diamondoids under pressure. The equation of state of adamantane and 1-chloroadamantane was determined up to 1.4 GPa from ultrasonic measurements of bulk modulus and is in good accordance with the previous equations developed from volumetric data. We measured the bulk and shear moduli and Poisson's ratio of adamantane and 1-chloroadamantane up to 1.4 GPa. The behaviors of elastic moduli are different for adamantane and 1-chloroadamantane. This indicates that the substitution of one hydrogen atom for chlorine significantly reduces both elastic moduli, particularly the shear modulus (≈30%). Although the pressure dependences of the bulk modulus B are almost linear and its pressure derivatives for adamantane and 1-chloroadamantane are close to each other (B' ≈ 10-12), a jump is hardly observed on the pressure dependence B(P) for adamantane at the transition from the plastic to ordered phase, whereas the pressure dependence of the bulk modulus for 1-chloroadamantane exhibits a jump of almost 17%. The experimental dependences of the bulk modulus and relative changes in the volume for both materials clearly demonstrate that the compressibility of 1-chloroadamantane is much higher for both phases. The Poisson coefficient calculated from our experimental data is larger for 1-chloroadamantane, having lower both bulk and shear moduli.
我们展示了一项关于金刚烷和1-氯金刚烷在高压（高达1.4吉帕）、不同温度（77 - 293开尔文）以及有序-无序转变情况下弹性性质的对比超声研究。超声方法提供了压力下类金刚石有序-无序转变的补充图像。通过对体模量的超声测量确定了金刚烷和1-氯金刚烷在高达1.4吉帕时的状态方程，且与先前从体积数据得出的方程高度吻合。我们测量了金刚烷和1-氯金刚烷在高达1.4吉帕时的体模量、剪切模量和泊松比。金刚烷和1-氯金刚烷的弹性模量行为不同。这表明用一个氯原子取代一个氢原子会显著降低两种弹性模量，尤其是剪切模量（约30%）。尽管体模量B的压力依赖性几乎呈线性，且金刚烷和1-氯金刚烷的压力导数彼此接近（B'≈10 - 12），但在金刚烷从塑性相转变为有序相时，几乎未观察到其体模量压力依赖性B(P)有跳跃，而1-氯金刚烷的体模量压力依赖性则呈现出近17%的跳跃。两种材料体模量的实验依赖性以及体积的相对变化清楚地表明，1-氯金刚烷在两个相中的可压缩性都高得多。根据我们的实验数据计算得出的泊松系数对于1-氯金刚烷更大，其体模量和剪切模量都较低。
