PDF《高温高压下碳 的状态方 程及》

252 报学理物压高第11卷obtain the entropy of solid ss=3Ⅳ 尼罗竿壬I一Wher0As is a correction termE6彐.3Ⅳ乃ln ee/T~1+geT+ s (6) 紧=-2γl+鲁EOs of liquid is developed frona that of sohd,that is based on a scalod liquid hcβ t ca- pacityE6彐cⅡ (r)― 1.5Rα/(l+αr)and an entropy of melting term Asm. Her0cⅡ o the val- ue for the solid,α =0.1,and r=T/Tm. Tm、 the me1ting temperature,determined by the Lindemonn meking law (7) The meltingˉ curve maxiFna under high pressure are not only discoved in graphite but 左lso known in other e1ements,tho intermetallic compounds,and the inorganic saltsE?彐.In all the known cases of1naxhna the solid at some high pressure also exhibits a solid-solid transition with a large volume change,such as the phase transition from graphite to diamond. RivlinE:彐and Furukawa et al【9彐haVe studied the melting of1nercury and tin and reported the existence of two separate ato∏ 】 ic distances i. liquid,correspond- ing to t、 vo speCies. This helps us to think that the melting processes of graphite are pr° bably more complicated than that of diamond due to its anisotropic structure. As is known that the covalence bond length of graphite lattice in the plane is O. 14nm,shorter than the atoΠ1ic distance of diamond lattice,whne the distance between neighbouring layers is O. 335nm,it is reasonable to think that the metal1ic bond and Van der waals f° rce between layers are destroyed first and the liquid turns into a Ⅱ 1ixed solution of atO】nic cluster(corresponding to graphite-hquid)and monatomiC fluid(corresponding to diamond-liquid),in a transition state of short-range-ordering and longˉ range-disorder- ing.As the temperature goes up and the pressure increases,the covalence bonds in the plane are destroyed gradually and finally it turns into complete monatomic fluid. Parameter Unit Graphite Diamond Parameter Un1t Graphite Diamond Po E映/ft 灬./R @ g/cms K 0.1TPa 3.51[】 ° ] 190.273[6〕 0.1331[6] 1411E6] 1.15(6] o.0[6] 1,l[6] 4.397[6] B∶ AsⅡ/R ge,./R 厶, K -ˉ 53,0315[6彐o,4636E6] 1280[6] 0.35[6] 1.156* 10ˉ 6E6] o.24[6] o.511[6 5.0[6] Kˉ

1 1.15E6彐Kˉ

1 1.156〉 《10ˉ 6[6) o. 24[6] 0.1[6] 3.65[6] l. 15E° ] 6.04* 10ˉ s[6] 约沙灿γ°抑‰B°o. 1tO] 2.9〉《10ˉ 6[!!] 1.19〉