High-pressure/high-temperature phase diagram of zinc

Abstract

The phase diagram of zinc (Zn) has been explored up to 140 GPa and 6000 K, by combining optical observations, x-ray diffraction, and ab initio calculations. In the pressure range covered by this study, Zn is found to retain a hexagonal close-packed (hcp) crystal symmetry up to the melting temperature. The known decrease of the axial ratio (c/a) of the hcp phase of Zn under compression is observed in x-ray diffraction experiments from 300 K up to the melting temperature. The pressure at which c/a reaches [Formula: see text] (≈10 GPa) is slightly affected by temperature. When this axial ratio is reached, we observed that single crystals of Zn, formed at high temperature, break into multiple poly-crystals. In addition, a noticeable change in the pressure dependence of c/a takes place at the same pressure. Both phenomena could be caused by an isomorphic second-order phase transition induced by pressure in Zn. The reported melt curve extends previous results from 24 to 135 GPa. The pressure dependence obtained for the melting temperature is accurately described up to 135 GPa by using a Simon-Glatzel equation: [Formula: see text], where P is the pressure in GPa. The determined melt curve agrees with previous low-pressure studies and with shock-wave experiments, with a melting temperature of 5060(30) K at 135 GPa. Finally, a thermal equation of state is reported, which at room-temperature agrees with the literature.

The Zinc Story under High Pressure

“…At higher pressures, however, one notices discernible differences among each data set. Early data by McWhan [18] and by Schulte, Nikolaenko and Holzapfel [19] as well as our data with ME-and MEW-PTM show smaller c/a ratio, whereas the recent data by Errandonea et al [12] show an upward shift. Our data with He-PTM smoothly change without any anomaly.…”

“…In the meantime, Takemura [17] reported an irregular change of the electrical resistance of Zn around 10 GPa similar to that observed by Lynch and Drickamer [16]. An x-ray diffraction study again suggested the existence of the c/a anomaly [12].…”

“…Since theoretical calculations are done for the state at 0 K, it is better to compare them with experiments conducted at low temperature. [12], squares [19], diamonds [18], and broken line [16]. Experimental uncertainty in c/a of our He-data is indicated by a gray curve.…”

“…Compression to extreme pressure and temperature conditions was also achieved by shock wave techniques in 1960's [9] [10]. The pressure-temperature phase diagram of Zn was studied by using a piston-cylinder apparatus [11] and most recently by a diamond-anvil cell coupled with laser-heating techniques [12]. In mid 1960's several groups were interested [29] indicated an anomaly occurring above 6.8 GPa, while another measurement by Klotz et al [30] showed no such evidence and casted doubts on the existence of ETT in Zn.…”

Anharmonic and Anomalous Trends in the High-Pressure Phase Diagram of Silicon

“…electronic structure and phonon calculations [1][2][3][4][5] and experimental measurements [6][7][8][9][10], incorporate information on novel phases [11][12][13][14] that serve as the backbone of highpressure materials science. As one of the most-abundant elements on Earth, silicon (Si) is of great interest to many fields encompassing industry [15], planetary science [16], geophysics [17], and high-energy-density (HED) physics [18,19].…”