Old results

The structures of amorphous carbon, located between two layers (each layer contents
32 atoms) of diamond has been investigated. Three samples:
1. 4 layers of moving atoms (128 moving atoms, in all 192 atoms, named 141)
2. 5 layers of moving atoms (160 moving atoms, in all 224 atoms, named 151)
3. 6 layers of moving atoms (192 moving atoms, in all 256 atoms, named 161)
has been heated to melt the central layers.
The the upper and the lower layers of each sample have been frozen
diamond (the heigth of each layer is 3.55 angstrom, this is 32 atoms in average). Meanwhile the central layers
( 4,5 or 6 layers) was heated to a temperatures 14000-30000 K, that is creates the temperature
gradient from edges to center of the sample. Then the central layers have been annealed
to the ambient temperature. The heigth of the edge layers is 3.55 angstrom, this is more
than the cutoff radius of the simulation 3 angsrom.
The systems reached the equilibrium during 2.5 ps
(5000 MD steps, each step - 0.5 fs). It is turned out that the structure of the amorphous carbon depends on size of
hot layer and on the temperature.
The results are shown below (the percentage of sp3, sp2 and sp bonded atoms are for amorphous
layers only, the bandgap is for whole sample, the temperature in the table is the temperature of
liquid sample, which has been annealed later). In the process of heating dimond in the central hot layers
experiences an amorphization and sp2 and sp bonded atoms appears in all the samples.
But during approaching to equilibrium sample 141 heated to 20000 K and sample 161 heated to 23000 K
returns to diamond mpeg movie), other samples remains partially or entirely amorphous. (see graphs)

                                          Sample 141

Temperature
percent of sp3 bonded atoms
percent of sp2 bonded atoms
percent of sp bonded atoms
Bandgap
18000 K
100
0
0
5.5eV
20000 K
95
5
0
4eV
23000 K
79
19
2
2eV
28000 K
74
23.5
2.5
1.3eV
30000 K
62
34
4
1eV



                                          Sample 151

Temperature
percent of sp3 bonded atoms
percent of sp2 bonded atoms
percent of sp bonded atoms
Bandgap
17000 K
96
4
0
5.4eV
20000 K
78
21
1
1.7eV
23000 K
71
29
0
0.4eV



                                          Sample 161


Temperature
percent of sp3 bonded atoms
percent of sp2 bonded atoms
percent of sp bonded atoms
Bandgap
14000 K
100
0
0
5.5eV
16000 K
89
10.5
0.5
2.6eV
17000 K
79
21
0
3eV
20000 K
74
26
0
2.3eV
23000 K
69
30
1
0.9eV



                                          Sample 171


Temperature
percent of sp3 bonded atoms
percent of sp2 bonded atoms
percent of sp bonded atoms
Bandgap
16000 K
100
0
0
5.3eV
18000 K
73
27
0.5
2.7eV
20000 K
69
30
1
1.6eV
22000 K
71
28
1
1.5eV
24000 K
56
42
2
0.4eV
26000 K
45
54
1
0eV

Here you can see the vizualizations of the sample 161 heated
to different temperatures and then annealed, the percentage of sp2 bonded atoms (blue balls) increases with the temperature.

14000 K
16000 K
17000 K
20000 K
23000 K