Gromnitskaya E L, Yagafarov O F, Stalgorova O V, Brazhkin V V, Lyapin A G
Institute for High Pressure Physics, Russian Academy of Sciences, Troitsk, Moscow Region, 142190, Russia.
Phys Rev Lett. 2007 Apr 20;98(16):165503. doi: 10.1103/PhysRevLett.98.165503. Epub 2007 Apr 19.
We present the ultrasonic study of gallium (Ga I) under high pressure up to 1.7 GPa, including the measurements of the density and elastic properties during phase transitions to Ga II and to a liquid state. The observed large drop of both bulk and shear moduli (by 30% and 55%, correspondingly) during the phase transition to Ga II, as well as the increase of the Poisson's ratio from typically "covalent" ( approximately 0.22) to "metallic" ( approximately 0.32) values, experimentally testifies to the coexistence of a molecular and metallic behavior in Ga I and to the disappearance of the "covalency" during the transition to Ga II. A high value of the pressure derivative of the bulk modulus for Ga I and the increase in the Poisson's ratio can be associated with the weakening of the covalency in compressed Ga I and considered as a precursor of the transition to normal metal.
我们展示了在高达1.7吉帕的高压下镓（Ga I）的超声研究，包括在向Ga II和液态转变过程中密度和弹性性质的测量。在向Ga II转变过程中观察到体模量和剪切模量均大幅下降（分别下降30%和55%），以及泊松比从典型的“共价”值（约0.22）增加到“金属”值（约0.32），这通过实验证明了Ga I中分子行为和金属行为的共存，以及在向Ga II转变过程中“共价性”的消失。Ga I的体模量压力导数的高值以及泊松比的增加可能与压缩Ga I中共价性的减弱有关，并被视为向普通金属转变的前兆。
