I did a simulation on the melting process of Cu nanoparticle. I found that the Cu NP starts to from the shell and gradually propagates to the inner core, but when the temperature approaches the melting point, the inner core suddenly shows some high thermally driven disorders and starts to melt before most of shell atoms. Is it possible to happen?
Dear Jiaqi:
Your question is the same with my problems of polyamorphic transitions. In macroscopic heterogeneous systems, phase transition order−disorder can occur under such a small change of a disturbing variable (T) that any measurements in the transition region are practically impossible. The transition between two states in this case is a manifestation of maximum cooperativity. In the ensemble of small systems (nanoparticle Cu), the transition between two states of water occurs under the final change in the disturbing variable. The description of phase transitions in a system with a finite number of particles has not been sufficiently developed up to the present time. You write “I found that the Cu NP starts to from the shell and gradually propagates to the inner core”. This example is similar to your “melting” transition. When “but when the temperature approaches the melting point, the inner core suddenly shows some high thermally driven disorders and starts to melt before most of shell atoms”. This example is similar to your polyamorphic transitions. The ensemble of small systems oscillates between states A and B because of the properties of the system itself. Extensive thermodynamic parameters of the ensemble of small systems in the transition region are linear combinations of thermodynamic parameters of the ensemble in states A and B.
I recommend to see our work on this subject and earlier. Liquid–liquid transitions were originally considered by Rapoport in 1967 in order to explain high pressure melting curve maxima of some liquid metals Rapoport, E. (1967). "Model for melting curve maxima at high pressure". J. Chem. Phys. 46 (2891): 1–5.
Double well type potential, which is proposed for polyamorphous systems. Mishima, O.; Mishima, Osamu (1998). "The relationship between liquid, supercooled and glassy water". Nature 396(6709): 329.
Regards
Dear Jiaqi:
Your question is the same with my problems of polyamorphic transitions. In macroscopic heterogeneous systems, phase transition order−disorder can occur under such a small change of a disturbing variable (T) that any measurements in the transition region are practically impossible. The transition between two states in this case is a manifestation of maximum cooperativity. In the ensemble of small systems (nanoparticle Cu), the transition between two states of water occurs under the final change in the disturbing variable. The description of phase transitions in a system with a finite number of particles has not been sufficiently developed up to the present time. You write “I found that the Cu NP starts to from the shell and gradually propagates to the inner core”. This example is similar to your “melting” transition. When “but when the temperature approaches the melting point, the inner core suddenly shows some high thermally driven disorders and starts to melt before most of shell atoms”. This example is similar to your polyamorphic transitions. The ensemble of small systems oscillates between states A and B because of the properties of the system itself. Extensive thermodynamic parameters of the ensemble of small systems in the transition region are linear combinations of thermodynamic parameters of the ensemble in states A and B.
I recommend to see our work on this subject and earlier. Liquid–liquid transitions were originally considered by Rapoport in 1967 in order to explain high pressure melting curve maxima of some liquid metals Rapoport, E. (1967). "Model for melting curve maxima at high pressure". J. Chem. Phys. 46 (2891): 1–5.
Double well type potential, which is proposed for polyamorphous systems. Mishima, O.; Mishima, Osamu (1998). "The relationship between liquid, supercooled and glassy water". Nature 396(6709): 329.
Regards
Dear Professor Yuri,
Thank you very much for your detailed information. It is really helpful. I will read the papers that you recommend. Thank you again!
Jiaqi
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