Comparative analysis of the thermosize effects of transition-metal clusters that are free or deposited onto graphene. Molecular dynamics simulation

Stability and thermal evolution of transition metal and silicon clusters

“…The variation of the nanoparticle structure as a function of the cooling rate was consistently analyzed. 71,74 As expected, transition to close-packed structures took place irrespective of the final cooling temperatures. However, detailed analysis demonstrated that at high final temperature, the content of Dh clusters decreased with a decrease in the cooling rate compared with their content at 77 K. This is related to the fact that the Dh structure was intermediate between the icosahedral and close-packed fcc and hcp structures under conditions where there was enough kinetic energy initiating internal rearrangements in the system.…”

“…However, detailed analysis demonstrated that at high final temperature, the content of Dh clusters decreased with a decrease in the cooling rate compared with their content at 77 K. This is related to the fact that the Dh structure was intermediate between the icosahedral and close-packed fcc and hcp structures under conditions where there was enough kinetic energy initiating internal rearrangements in the system. 74 It follows from the data of Table 2 that the most favourable conditions for the formation of clusters with close-packed fcc or hcp structures appeared in the system with a cooling rate of 0.005 K ps 71 and a final cooling temperature of 373 K. The calculated Cu7Cu bond energies for these regular packings (with interatomic distances of 0.235 ± 0.270 nm) are limited to the range of 2.5 ± 2.8 eV per atom; the bond energies for larger and more stable clusters with a regular structure were 3.15 ± 3.25 eV per atom in the low-temperature region (200 ± 400 K).…”

“…4); 74,77,78 Ð the formation process of a large cluster comprises all of the stages with relaxation: nucleation, condensation, growth of single clusters, cluster collisions and coalescence (Fig. 5).…”

“…5). 74,79 The relaxation of the model system activated by the stored energy of clusters and coordination restructuring of diplos resulted in the formation of coherent boundaries within the cluster. During each relaxation step, a coherent structure formed as a result of thermally activated diffusion rearrangements.…”

The comparative analysis of dependence on temperature of diffusion and strength characteristics of graphene reinforced Al, Ni and Ti films

“…Однако термостабильность и прочностные характеристики интерфейсов (модули сдвига) даже с двумя пленками Me / G / Me повышаются на 90 % с дополнительным армированием графена -об-кладками (G / Me / G / Me / G), гасящими терморазупорядо-чение (в Al до 2100 K, в Ti и Ni до 3400 K). Для всех рассмотренных систем Ме / G рассчитанные по среднеквадратичным смещениям компоненты диф-фузии в интерфейсных плоскостях X-Y, D xy и нормали вдоль оси Z, D z по-разному зависели от температуры на-грева, отражая разный характер изменения электронной структуры, естественно энергии адгезии и типа сорбции в интерфейсах [3,8]. Для интерфейсов с физической ад-сорбцией изменение диффузионной активности отлича-лось плавностью с заметным ростом для Al / G / Al (с двой-ным покрытием) в области ~1800K, но разной степенью немонотонности, в то же время, для хемосорбционных интерфейсов, сформированных при гибридизации π z -d z -орбиталей, медленный рост на начальных этапах нагрева уже в области высоких температур (~2000 K) ме-нялся резким увеличением обеих компонент коэффици-ентов диффузии.…”