With respect to your raising the ideas about red mercury, several ideas occur.
First, let us recall that in the early days of the Manhattan Project, December 1940 into January1941, and on, the Committee used code words for the active materials of the project, and for fission, especially fission with a k> 1. k > 1 being a self-sustaining fission chain reaction, e.g. the neutron flux increasing in a structure.
These code words were, for example moonshine for fission, copper for Pu239, magnesium for U235, and tube alloy for U238 (both in irradiated and natural states). Similarly, the various RADAR bands were assigned non-serialized designations that endure to this day. And there are numerous related examples, Manhattan District itself, for example.
I expect that our Russian brothers did and do the same, and it seems to me that this obfuscatory tradition probably continues with regard to red mercury.
I dont think its a mercury derivative at all I think the label mercury is a sort of metaphor, suggested by the proximity of the planet Mercury to the Sun and also, perhaps, by the association in the mind between temperature measurement and mercury. How high is the mercury? we say. Indeed. Very cute. Mercury seems to be an obscure and oblique reference to high temperatures and, therefore, perhaps, to fusion. And the name may well have been a project name, later adapted to the product itself. As to red, this is the color universally used to signify danger, and often to signify heat as well. Also apropos, if we assume the stuff exists. Assuming this, Ill call it RM.
The story is that RM is shock-sensitive ballotechnic. I suspect that this too is related only in an obscure somewhat metaphorical way to the material. I suspect that RM is a stimulated gamma emitter. There is, as you know, online evidence of serious research on such materials. It is, possibly, hafnium 178m2 or another substance that, similarly, can be pumped to a high state and collapsed nicely with the attendant emission of high energy photon(s). I speculate that, stimulated by the input shock of a burst of gamma or possibly ionizing radiation from an electronic or radioactive trigger, the nuclei of the pumped RM atoms, if they exist, become extremely unstable and rapidly (<1 nano-second perhaps) collapse to a lower energy level, releasing high energy photons in the form of gamma with, presumably, an energy level >5000eV. Open sources cite gamma radiation in excess of this level.
The ignition threshold for deuterium-tritium fusion (D+T) is, as I understand things, 5000 eV. (continued...)