Hidden negative linear compressibility in lithium L-tartrate†

By decoupling the mechanical behaviour of building units for the first time in a wine-rack framework containing
two different strut types, we show that lithium L-tartrate exhibits NLC with a maximum value, Kmax = 21 TPa1
,
and an overall NLC capacity, wNLC = 5.1%, that are comparable to the most exceptional materials to date.
Furthermore, the contributions from molecular strut compression and angle opening interplay to give rise to
so-called ‘‘hidden’’ negative linear compressibility, in which NLC is absent at ambient pressure, switched on at
2 GPa and sustained up to the limit of our experiment, 5.5 GPa. Analysis of the changes in crystal structure using
variable-pressure synchrotron X-ray diffraction reveals new chemical and geometrical design rules to assist the
discovery of other materials with exciting hidden anomalous mechanical properties.