Nucleation
Nucleation is the first step in the formation of either a new thermodynamic phase or a new structure via self-assembly or self-organization. Nucleation is typically defined to be the process that determines how long an observer has to wait before the new phase or self-organized structure appears. Nucleation is often found to be very sensitive to impurities in the system. Because of this, it is often important to distinguish between heterogeneous nucleation and homogeneous nucleation. Heterogeneous nucleation occurs at nucleation sites on surfaces in the system. Homogeneous nucleation occurs away from a surface.
Characteristics of nucleation
Nucleation is usually a stochastic process, so even in two identical systems nucleation will occur at different times. This behaviour is similar to radioactive decay. A common mechanism is illustrated in the animation to the right. This shows nucleation of a new phase (shown in red) in an existing phase (white). In the existing phase microscopic fluctuations of the red phase appear and decay continuously, until an unusually large fluctuation of the new red phase is so large it is more favourable for it to grow than to shrink back to nothing. This nucleus of the red phase then grows and converts the system to this phase. The standard theory that describes this behaviour for the nucleation of a new thermodynamic phase is called classical nucleation theory.
Podcasts:
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by Nellie McKay
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by Cardiacs
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by Delfinai
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by Waitresses
No Equality
by: Nellie McKayThere's no equality here
There's no equality anywhere
And every failing face
Is quickly replaced
By one you can't lose
It's an illusion
I'll even do revolution
That's never meant to occur
Won't happen to her
Won't happen to you
And you let me down slowly
Let me down slow and you turned me around
Let me down easy
Let yourself go, now you're goin' to town
Baby, baby, can't you see
What this hypocrisy is doin' to me?
We should've kicked over the ladders
From the start
You used to be my lover
You used to be my soul, soul brother
I used to believe
That you could conceive
Conceive with my love
But you let me down slowly
You let me down slow and you turned me around
Let me down easy
Let yourself go, now you're goin' to drown
Baby, baby, can't you see
What this absurdity is doin' to me?
We should've kicked over the ladders
From the start
There's no equality
Nobody knows the trouble I've seen
No one supposes just how mean I can be
I play the victim and I really care
And all I've ever wanted is
Everything I'm gonna have
There's no equality here
There's no equality on earth I fear
There are so many [Incomprehensible]
The boss and the border
It's me or it's you
That's why I let you down slowly
Let you down slow and I turned you around
Let you down easy
Let myself go, now we're both set to drown
Baby, baby, can't you see
What this futility is doin' to me?
We should've kicked over the ladders
From the start