The meaning of temperature in nano particles

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Discussion Overview

The discussion centers on the concept of temperature in relation to nanoparticles, particularly focusing on how temperature is defined and measured when dealing with systems that contain a low number of atoms. Participants explore the implications of statistical mechanics and thermodynamics in these small systems.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that temperature is fundamentally a thermodynamic property reliant on the statistical number of particles, raising questions about its applicability to nanoparticles with few atoms.
  • One participant quotes a professor stating that temperature is something measured with a thermometer, suggesting that the meaning of temperature diminishes with smaller statistical ensembles.
  • Another participant references theoretical discussions on temperature, entropy, and their unclear relationships, expressing uncertainty about the understanding of entropy itself.
  • It is suggested that while temperature may lose its meaning in isolated systems with few degrees of freedom, there exists a microscopic understanding of heat that remains relevant in nano-electronic and thermo-electric devices.
  • A participant elaborates that in practical scenarios, small systems are often coupled to an environment with many degrees of freedom, leading to a statistical distribution that defines temperature based on the environment's temperature.
  • Brownian motion is cited as a classical example where a heavy particle's temperature is influenced by interactions with lighter particles in its environment, leading to a Boltzmann distribution over time.
  • A quantum example involving a two-level system (qubit) interacting with the environment is also mentioned as a means to "obtain a temperature."

Areas of Agreement / Disagreement

Participants express differing views on the meaning and relevance of temperature in small systems, with some arguing it becomes less meaningful while others maintain that it can still be defined through environmental interactions. The discussion remains unresolved regarding the implications of these differing perspectives.

Contextual Notes

Limitations include the dependence on definitions of temperature and the statistical nature of small systems, as well as the unresolved relationship between temperature and entropy.

saray1360
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Hi,

I always had the idea that temperature is a thermodynamical property which means that the statistical number of particles are important in measuring the relative temperature of the system.

But, what happens when it comes to nano particles in which we have low numbers of atoms. How temperature is described then?

Regards,
 
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To quote an old prof of Atomic & Molecular Physics I know: "Temperature is something you measure with a thermometer."

The smaller the statistical ensemble you've got, the less meaningful it is.
 
You can get some further insights here:

http://en.wikipedia.org/wiki/Temperature#Theoretical_foundation

which discusses the theoretical temperature of the vacuum and an entropy interpretation of temperature...but the relationship between these, and also information for that matter, is not at all clear to me...in fact, I am unsure anyone really understands entropy to this day...
 
Temperature might lose its meaning , but there's still a sound microscopic understanding of "heat".

And even in nano-electronic devices, or thermo-electric devices I cannot think of an example where the number of "electrons" or "atoms" involved defying the concept of temperature.

I don't think this is a practical issue. It's just academic
 
saray1360 said:
Hi,

I always had the idea that temperature is a thermodynamical property which means that the statistical number of particles are important in measuring the relative temperature of the system.

But, what happens when it comes to nano particles in which we have low numbers of atoms. How temperature is described then?

Regards,

As far as I know, it is not meaningful to talk about temperature of an isolated system of very few degrees of freedom. However, in reality all such systems are (to some extent) coupled to an environment which has many degrees of freedom. This coupling will eventually lead to a statistical distribution for the small system with a temperature defined by the temperature of the bath (environment). The time scale at which this happens depends on the coupling (interaction) between the system and the bath.

EDIT:
I think Brownian motion is a good classical example. Here we are talking about a heavy particle interacting with bunch of lighter particles (forming an environment or bath). If the heavy particle were isolated it would not make any sense to ask "What is the temperature?". However, due to the interaction with the environment which can be described by random kicks (stochastic force) the properties of the particle (velocity and position) become randomized with a statistical distribution which after long enough time becomes the Boltzmann distribution with temperature of the bath.

A quantum example would be a two-level system (qubit) interacting with the environment to "obtain a temperature".
 
Last edited:

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