3.1 Evolution of potential energy (PE) and total number of MDNP
The PE development of MDNP could be applied for judging if the chemistry reactions reach balance, and the sum of MDNP could be applied for assessing the thermolysis level of MDNP. For that reason, the PE of MDNP is subjected to analysis posterior to emulations. PE development of MDNP varies with time at different heating rates are shown in Figure. 3.
Figure. 3 shows the development of total PE with time at different heating rates. MDNP gradually absorbs heat to reach primary decomposition energy at different heating rates. With increasing temperature, the decomposing of MDNP generates a series of middle and eventual products and releases a large amount of heat, so the potential energy decreases significantly. Moreover, if the temperature is elevated, the maximal results of PE and the PE reduction rate will be higher. With the increase of temperature, the greater the stability value of PE, the shorter the time for PE to stabilize. The curves of MDNP show that at 10 K·ps-1, 15 K·ps-1 and 20 K·ps-1, MDNP molecules are converted into intermediate products via decomposition in 178.02 ps, 110.60 ps and 100.00 ps, separately, revealing that faster heating rates trigger more rapid thermolysis of MDNP. The time evolution of consumption of MDNP at various temperatures is displayed in Fig. 4.
3.2 Evolution of intermediate products
In the process of MDNP thermolysis, substantial middle and eventual products were produced. The generative time and the quantity of intermediate and eventual products are pivotal for the investigation of the decomposing process of MDNP. The generative times of the primary intermediate generated by MDNP decomposition are shown in Table. 1-3. Development of the primary intermediate product quantity (C7H7O5N2, C7H6O4N2, C7H5O5N2, C7H5O4N2, HON, NO, NO2) generated by MDNP decomposition at 10 K·ps−1, 15 K·ps−1 and 20 K·ps−1 are displayed in Figure. 5.
Table 1
Main intermediate products generated by MDNP decomposition at 10 K·ps−1
Products
|
Time/ps
|
Products
|
Time/ps
|
MDNP
|
0
|
C7H5O4N2
|
121.52
|
C7H7O5N2
|
51.02
|
HON
|
152.38
|
C7H6O4N2
|
124.74
|
NO
|
143.18
|
C7H5O5N2
|
51.02
|
NO2
|
121.36
|
Table 2
Main intermediate products generated by MDNP decomposition at 15 K·ps−1
Products
|
Time/ps
|
Products
|
Time/ps
|
MDNP
|
0
|
C7H5O4N2
|
82.58
|
C7H7O5N2
|
40.18
|
HON
|
96.46
|
C7H6O4N2
|
85.18
|
NO
|
92.80
|
C7H5O5N2
|
40.2
|
NO2
|
83.46
|
Table 3
Main intermediate products generated by MDNP decomposition at 20 K·ps−1
Products
|
Time/ps
|
Products
|
Time/ps
|
MDNP
|
0
|
C7H5O4N2
|
60.76
|
C7H7O5N2
|
16.54
|
HON
|
93.60
|
C7H6O4N2
|
60.82
|
NO
|
79.02
|
C7H5O5N2
|
16.54
|
NO2
|
62.56
|
We could deduce from Figure. 5 that the quantity of the middle products C7H7O5N2, C7H6O4N2, C7H5O5N2, C7H5O4N2, HON, NO and NO2 molecules initially raised and afterwards progressively dropped to 0 with the development of the reaction, where high-frequency reactions primarily happened between those middle product molecules till the forming of eventual steady products. The chronology order of the middle product occurrence was C7H5O5N2, C7H7O5N2, C7H5O4N2, C7H6O4N2, NO2, NO, HON. The order of the maximum number of intermediates is C7H5O4N2, C7H5O5N2, NO2, HON, NO, C7H7O5N2, C7H6O4N2 at 10 K·ps−1. The order of the maximum number of intermediates is C7H5O5N2, NO2, C7H5O4N2, HON, NO, C7H6O4N2, C7H7O5N2 at 15 K·ps−1. The order of the maximum number of intermediates is C7H5O4N2, C7H5O5N2, HON, NO2, NO, C7H6O4N2, C7H7O5N2 at 20 K·ps−1. The order of the number of the maximum intermediates of intermediates under different heating rates is different, in that the reaction time is different at each heating rate, the maximum number of intermediates is different.
C7H7O5N2, C7H6O4N2, C7H5O5N2 and C7H5O4N2 were the primary middle products in the initial thermolysis process of MDNP. With the development of thermolysis, HON, NO and NO2 turned into the primary middle products. The entire middle products nearly vanished posterior to 2700 K. The quantity of N2, CO2, H2O, H2 and NH3 was elevated with the development of the decomposition, revealing that the production of N2, CO2, H2O, H2 and NH3 molecules were ongoing in the entire decomposing process.
3.3 Evolution of final products
The entire eventual products were small molecule products like N2, CO2, H2O, H2, NH3, etc. The generation times of the main eventual products produced by MDNP thermolysis are shown in Table. 4-6. The development of the quantity of the primary eventual products (N2, CO2, H2O, H2, NH3) produced by MDNP thermolysis are displayed in Fig. 6. We could deduce from the emulation outcomes that the chronology order of the final product occurrence was H2O, H2, CO2, N2, NH3 at 10 K·ps−1. We could deduce from the emulation outcomes that the chronology order of the final product occurrence was H2O, H2, N2, NH3, CO2 at 15 K·ps−1 and 20 K·ps−1. The order of the maximum number of eventual products was H2O, N2, H2, CO2, NH3 at 10 K·ps−1 and 15 K·ps−1. The order of the maximum number of final products is H2O, N2, NH3, H2, CO2 at 10 K·ps−1 and 15 K·ps−1.
Table 4
Main eventual products produced by MDNP thermolysis at 10 K·ps−1
Products
|
Time/ps
|
Products
|
Time/ps
|
MDNP
|
0
|
H2
|
129.66
|
H2O
|
99.70
|
CO2
|
173.50
|
N2
|
183.00
|
NH3
|
207.48
|
Table 5
Main eventual products produced by MDNP thermolysis at 15 K·ps−1
Products
|
Time/ps
|
Products
|
Time/ps
|
MDNP
|
0
|
H2
|
123.42
|
H2O
|
76.70
|
CO2
|
139.66
|
N2
|
137.76
|
NH3
|
138.80
|
Table 6 Main eventual products produced by MDNP thermolysis at 20 K·ps−1
Products
|
Time/ps
|
Products
|
Time/ps
|
MDNP
|
0
|
H2
|
93.96
|
H2O
|
61.22
|
CO2
|
117.26
|
N2
|
106.68
|
NH3
|
116.50
|
The entire middle products nearly vanished posterior to 135 ps emulations at 20 K·ps−1. The quantity of N2, CO2, H2O, H2 and NH3 was elevated with the development of the decomposition, revealing that the production of N2, CO2, H2O, H2 and NH3 molecules are undergoing the entire decomposing process. During the first phase of MDNP thermolysis, there wasn't any production of H2 and CO2, which revealed that the decomposing of MDNP didn't generate H2 and CO2 straightly, and H2O and CO2 were primarily generated by the reactive process between middle products. H2O occurred at 61.22 ps at 20 K·ps−1, revealing that some H2O were possibly produced by MDNP straightly. We could come to the conclusion from Figure. 6 that with the rise of temperature, the quantity of N2, CO2, H2O, H2, NH3 was elevated, unveiling that high-temperature facilitated the production of gas products.
For intermediate products, the main decomposition paths of C7H7O5N2 are (1) C7H6O5N2 + HON → C7H7O6N3, (2) C7H7O6N3 → C7H7O5N2 + ON. The main decomposition paths of C7H6O4N2 are (1) C7H6O5N2 → C7H5O4N2 + HO, (2) C7H5O4N2 + HON → C7H6O5N3, (3) C7H6O5N3 → ON + C7H6O4N2. The main decomposition paths of C7H5O5N2 are (1) C7H6O5N2 → C7H5O4N2+ HO, (2) C7H5O4N2 + O2N → C7H5O6N3, (3) C7H5O6N3 → C7H5O5N2 + ON. The main decomposition path of C7H5O4N2 is C7H6O5N2 → C7H5O4N2 + HO. The main decomposition paths of HON are as follows: (1) H2O2N → HON + HO, (2) H3O2N → H2O + HON, (3) C7H5O4N2 → C7H4O3N + HON. The main decomposition paths of NO are as follows: (1) H2O2N → H2O + ON,(2) HO2N → ON + HO༌(3) C7H5O5N3 → C7H5O4N2 + ON. The main decomposition paths of NO2 are (1) C7H5O5N2 → C7H5O3N + O2N༌(2) C7H5O6N3 → O2N + C7H5O4N2༌(3) H2O3N → H2O + O2N.
For final products, the main decomposition paths of H2O are (1) H2O2N → H2O + ON, (2) H3O2 → H2O + HO, (3) H2ON2 → H2O + N2. The main decomposition paths of N2 are (1) H2ON2 → H2O + N2, (2) HON2 → N2 + HO, (3) CO2N2 → N2 + CO2. The main decomposition paths of H2 are (1) H3O → H2 + HO, (2) H2ON → H2 + ON. The main decomposition paths of CO2 are as follows: (1) CO2N2 → N2 + CO2, (2) CO3N → CO2 + ON, (3) CH3O2N → H3N + CO2. The main decomposition paths of NH3 are as follows: (1) H4ON → H3N + HO, (2) H5ON → H2O + H3N, (3) H3ON2 → H3N + ON.