On the Surface Properties of Nano-Diamond

M.N. Magomedov

Institute for Geothermal Research of Daghestan Scientific Center RAS,
Chamil str., 39a, Makhachkala, 367030, RUSSIA, E-mail: mahmag@dinet.ru

By method, which was described in works [1-3], it were studied the dependencies: of the specific surface energy , of the isochoric temperature derivative of specific surface energy (  /  T)V, and of the surface pressure Psf versus  size, surface’s shape, and temperature of nano-diamond with the free surface. Nanocrystal has the form of a rectangular parallelepiped with the square base faceted by the {100} planes, and number of atoms in which is varied from 5 to . Interatomic interaction was described by the Mie-Lennard-Jones pair potential, with parameters are determined in work [4]. We considered the Debye temperature, and the Grüneisen parameter are independent vs the temperature and calculated them by the method, which described in work [5].
For macro-diamond is received: (20 K) = 6118.2 [10– 3 J/m2], ( / T)V(20 K) = 0; 
(4300 K) = 5710.8 [10 – 3 J/m2];      ( / T)V(4300 K) = – 106.89 [10 – 6 J/m2 K].
It were calculated the isothermo-isomorphic size dependencies of next functions: (N), ((N)/T)V, f, of the surface pressure Psf(N), and of the “Laplase surface pressure” Pls(N) for nano-diamond at temperatures from 20 K to 4300 K. Results have shown that at this conditions the surface energy is positive:  > 0. It point at the impossibility of the fragmentations of nano-diamond at the temperatures till to 4300 K. The surface pressure: Psf(N)  N – 1/3, is turned out to be much smaller (in 30 time !), than  “Laplase pressure”: Pls  N – 1/3, for the same nanocrystal under this values of the temperature, density and number of atoms. With growing of the temperature from 20 K to 4300 K the isotherm of “Laplas pressure” Pls(N) is lowered relatively little, but the isotherm of resulting surface pressure Psf(N) is lowered enough noticeably and even, having changed form of size dependence, at high temperatures it is fall in to region of the stretching of small nanocrystals.
This work was supported by RFBR (Project No. 09 – 08 – 96508), and by Programs of the Presidium of RAS (Project No. 12.1.19).

References

[1] M.N. Magomedov. Physics of the Solid State. 46 (2004) 954.
[2] M.N. Magomedov. High Temperature. 43 (2005) 870.
[3] M.N. Magomedov. High Temperature. 47 (2009) 45.
[4] M.N. Magomedov. Russian Journal of Inorganic Chemistry. 49 (2004) 1906.
[5] M.N. Magomedov. Physics of the Solid State. 45 (2003) 32.