常规温度下HgS相变过程中热力学及晶体结构变化研究

Calculation of Thermodynamic and Crystal Structure Changes of HgS Phase Transition at Conventional Temperature

天然矿物朱砂呈色鲜艳、化学性质稳定,属于常用红色天然矿物颜料,在古今中外各类出土文物中均有发现.长期老化后朱砂颜料褪色或变黑,影响了文物历史、艺术、科学价值的发掘.对朱砂变色机理的研究能为文物原貌恢复与预防性保护提供科学依据.朱砂经相变转化为黑色β-HgS的过程被认为是朱砂变色的可能机理之一.采用密度泛函理论对α-HgS及其同质异形体的晶体结构与性质进行了理论计算,探究了HgS同质异形体间相互转化过程中晶胞形态变化和热力学变化.结果表明,常温常压下α-HgS到β-HgS相转化无法进行,颜料变色由外界其他因素导致.

Cinnabar is a commonly used red natural mineral pigment in various kinds of cultural relics discovered around the world due to its bright color and stable properties.Cinnabar pigments fades to dark red or even black after long-term aging,affecting further research on the historical,artistic and scientific values of cultural relics.The study on the mechanism of cinnabar discoloration can provide a scientific basis for the restoration and preventive protection of cultural relics.The phase transformation from cinnabar to blackβ-HgS is one of the possible mechanisms of cinnabar discoloration.The theoretical calculation based on density functional theory was carried out to reveal the crystal structure and properties ofα-HgS(main component of cinnabar)and its paramorphs.Crystallographic alteration and thermodynamic in the phase transformation process among HgS paramorphs were investigated.The results indicated that it is impossible forα-HgS to transform intoβ-HgS at room temperature and pressure,and the discoloration of cinnabar was caused by other external factors.