LAUSR

There is a lack of consensus on the crystal structure and polymorphism of Cu(I)-TCNQ, even though an enormous work and great achievements have been reported along decades. This motivated us to perform a crystal structure prediction study (by using FFCASP) combined with total energy calculations at DFT-D level. The ensemble of the optimized structures falls in two distinct regions based on the energy-density phase space. Our predictions located the thermodynamic phase (as a global minimum) and a conformationally similar local minimum structure to the experimentally proposed phase I, in the low- and high-density regions respectively. The Rietveld refinement of P2 1 2 1 2 local minimum structure to the experimental XRD pattern resulted in a structure with a density between the two regions. This polymorph, the kinetic product, becomes a high energy local minimum structure after the full geometry optimization, being 35.03 kJ/mol above the global minimum. In addition, we found that the transition from the high-...