Nuclear Fusion with extremely high pressure and low temperature Theoretically, if we just create a high pressure with low (room 20C) temperature, at some point nuclear fusion can be started.
Is there any research on this topic, how high should be this pressure for different type of reaction?
Maybe someone has some numbers in mind, how many GPa should we have to achieve it?
UPDATE:
I made my own calculation after all comments which I got.
I got a number $10^{21}$ Pa from thermodynamics of ideal gas. Of course it is approximation. Let's say for Deuterium-tritium we have to give energy 0.1 MeV for 2 atoms to start fusion, which means from electrostatic point of view distance between nucleus $1.44\times10^{-14}$ (14 femtometers) as @John Rennie answered. If I calculated how many atoms will fit in 1 $m^{3}$, if distance between atoms will be 14 femtometers, I will get $N=3.4\times10^{41}$ atoms. Then from $PV=\frac{N}{N_{a}}RT$ if I assume $V=1 m^{3}$ I get $P=1.4\times10^{21}$ Pa and density $2.24\times10^{21} \frac{kg}{m^{3}}$. Which is still $10^{5}$ times more than pressure in the core of the Sun. And if we consider real gas, might be number will be bigger.
Maybe in the future, if they will find another reaction with much less energy (less then 0.1MeV) it would be possible. Might be quantum tuneling can help a little bit :)
 A: From memory the potential barrier for deuterium tritium fusion peaks at around $3$ femtometres.
Suppose we take the deuterium-tritium distance as $r$ then the electrostatic force between the nuclei is:
$$ F = \frac{ke^2}{r^2} $$
and we get can a pressure by dividing this by the area of a sphere with radius $r$ to get:
$$ P = \frac{ke^2}{4\pi r^4} $$
You should regard this as a very rough estimate, but it should be immediately apparent the the $r^{-4}$ dependence is going to be a killer because it rises very rapidly for small $r$. If we take $r$ to be $10$ femtometres we get a pressure of about $10^{28}$ Pa. This is so ridiculously large that even given the rough nature of our estimate it's obvious that this approach is not going to work. The pressure at the centre of the Sun is only around $3\times 10^{16}$ Pa.
A: As @John Rennie said, you will need a very high pressure if you want you atoms to be forced to be close enough to actually touch their respective barriers. What you describe sounds more as what happens in a neutron star in superextreme conditons.
To start fusion in a more conventional way, each nucleus must have an energy of 0.1 MeV. Acoding to Boltzmann, $E_p=k_B*T$ is the energy of each particle at a certain temperature. At room temperature this energy is 25meV, several orders of magnitude lower than that.
However, if you increase the pressure of this gas at room temperature and keep the temperature constant, each particle energy remains the same. The fact that you have more pressure means more particles are contained in the gas, but on average each particle will have the same energy (25meV) as stated by Boltzmann's law, and won't be able to break the barrier of fusion.
