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. For example, if a volume of water is cooled (at atmospheric pressure) below 0 °C, it will tend to freeze into ice, but volumes of water cooled only a few degrees below 0 °C often stay completely free of ice for long periods. At these conditions, nucleation of ice is either slow or does not occur at all. However, at lower temperatures ice crystals appear after little or no delay. At these conditions ice nucleation is fast. Nucleation is commonly how first-order phase transitions start, and then it is the start of the process of forming a new thermodynamic phase. In contrast, new phases at continuous phase transitions start to form immediately.
Nucleation is often found to be very sensitive to impurities in the system. These impurities may be too small to be seen by the naked eye, but still can control the rate of nucleation. 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.
Consider the decay in a quantum field theory from a metastable vacuum to the "true" vacuum.
Here's i my understanding:
1. For a scalar field potential U(\phi), the transition amplitude is finite per unit volume for a finite energy splitting between the 2 classical minima of the potential...
Hi there, I'm very stuck on this problem when approaching it like this. I know I could use the Landau Criterion for rotons but that's not accepted here, it wants the approach to come from the uncertainty principle.
My thinking is along these lines:
There will be a change in chemical potential...
I am trying to understand the nucleation process of salt deposits, if someone here could give me a point in the right direction it would be really appreciated.
I read that if you have a water rich in sulfates, and mix with a water rich in barium ions, calcium ions or strontium ions, that a seed...
It seems like having the ability to become supercooled below their melting point is the default for liquids (at least liquids without suspended particles, without many interfaces, and without other perturbations). Are there any liquids that don't supercool at all? Or if not, are there any...
A new form of ice has been discovered dubbed ice VII:
https://arstechnica.com/science/2018/10/weird-water-phase-ice-vii-can-grow-as-fast-as-1000-miles-per-hour/
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.155701
I have found some odd Nucleation points that appear inside of the top area of a bottle of Diet Pepsi (the area right near the cap as shown in pictures below). The nucleation sites appear either as soon as you open the bottle, or after the first drink (I will test this once more and see exactly...
Hey all,
I was wondering if anyone could help me with a basic BWR question. Why do BWRs have shrouds?
From what I've been able to find, this is a for "uniform cooling" but that's about it.
My guess is that there are some thermal hydraulic benefits around maintaining nucleate boiling. Is...
Consider that the criterion for bubble nucleation (in a field theory) is the following:
$$\exp(-S_{3}/T) \gtrsim \frac{3}{4\pi} \left(\frac{H}{T}\right)^{4} \left(\frac{2\pi T}{S_{3}}\right)^{3/2},$$
where ##S_3## is the three-dimensional action of the theory and ##H## is the Hubble scale.
1...
In this article https://en.wikipedia.org/wiki/False_vacuum#Bubble_nucleation it says that "In the theoretical physics of the false vacuum, the system moves to a lower energy state – either the true vacuum, or another, lower energy vacuum – through a process known as bubble nucleation." What is...
Homework Statement
A cylindrical pill-like solid cluster of radius r nucleates from the vapor phase on a dislocation that emerges from the substrate. The free-energy change per unit thickness is given by
\Delta G = \pi r^2 \Delta G_v + 2 \pi r \gamma + A - B lnr
Where A - Blnr represents...
1. Is nucleation a phenomenon that occurs in all phase change (freezing/melting, evaporation/condensation)?
2. I've always read evaporation/condensation described as a liquid-vapour interface phenomenon (water molecules going entering-leaving the interface at equal rates in equilibrium). If...
Hi everyone,
I'm having trouble understanding a problem on CNT in 2d.
I'm given the equation
\Delta G = \frac{4}{3} \pi R^3 \rho_s \Delta \mu + 4\pi R^2 \gamma
for nucleation in 3d. Here mu is the difference in chemical potential between the solid and liquid phase, R is the radius...
I'm currently working on a project for a code that does umbrella sampling of a 2-D Ising model [size LxL of a magnet (analyzing up or down spins)]. The next step is to take my code to analyze a nucleation region and its growth by varying the temperature above critical. Before I even attempt to...
Hello guys , I'm a medical student , and I'm very fascinated by this Mentos and diet cola experiment , however i do not understand it completely and i would like to know the followings
-From my understanding it happens because of Heterogeneous Nucleation , is that right ? Then i do not...
Technical question about nucleation of beer!?
I work as a barman and am also a physics student. But I just can't seem to get my head around something: I understand that beer (referring to lager really) consists of water with CO2 dissolved in it with other, irrelevant, stuff also. You cannot see...
Hi!
I seem to be out of the loop at work. Too embarrass to ask my coworkers to explain it to me.
Can anyone explain what nucleation and seeding is?
Our process is basically a precipitation process where copper is precipitated by reacting Ca(OH)2 to Cu(OH)2. We have a sedimentation tank...
Homework Statement
Assume for the solidification of nickel that nucleation is homogeneous, and the number of stable nuclei is 10^6 nuclei per cubic meter. Calculate the critical radius and the number of stable nuclei that exist at the following degrees of supercooling: 200 K and 300 K...
Hi everyone,
Question
In metals, for homogeneous nucleation, activation free energy required for the formation of a stable nucleus are different when the nucleus are considered as a cube and considered as a sphere and the relation between them is energy for cube is almost double of the...
for my thermodynamics class we have a question where we need to graph the evaporation and condensation rates as functions of g, the number of g-mers in our droplet of radius r. but condensation and evaporation are given in terms of r... is there an equation to relate r and g?
i've looked...