  Metal superhydrides such as CaH6, YH9 and LaH10 et. al., show a good
potential to achieve room-temperature superconductivity and have been studied
intensively in the past decade. With the help of diverse crystal structure
prediction (CSP) methods, structures of binary superhydrides MHn with varying
metals across the periodic table and many compositions up to n=24 have been
thoroughly searched, and their properties and superconductivity thoroughly
studied, without bringing any unexpected breakthrough. While the usual chemical
space spanned by the integer H/M ratios n has almost been exhausted and many
ternary superhydrides, consisting of two metals, have also been explored, there
are large areas in the composition space that have not been systematically
explored. For example, no explicit rule excludes a non-integer H/M ratio in the
binary. However, a thorough structure search of MxHy, as well as ternary
superhydrides, is a tremendous task and cannot reach the extent of the study of
binary superhydrides with current CSP methods. Based on our recent template
theory that explains the stability of metal superhydrides as the result of a
"template effect" of metal lattices, we conducted a systematic search of MxHy
and ternary superhydrides in two steps including the identification of the
efficient templates and the assembly of superhydrides. With the help of this
method, we identified many new superhydrides, including more than 30 complex
clathrate superhydrides, many have more than 50 atoms in the primitive cell.
The method also shows good potential to search ternary superhydrides in large
scale.
