Acid solvation states are investigated in the recently discovered mixed ether:acid crystalline solids. The solids are simulated using on-the-fly molecular dynamics as implemented in the density functional code QUICKSTEP employing Gaussian basis sets. The solids are shown to display a remarkably broad range of acid solvation states, depending on the ether:acid ratio, including proton sharing in the 1:1 case, proton transfer to the ether in 1:2, and perturbed molecular acid in 1:6. The observed variation of the infrared spectra with the composition is accounted for qualitatively with the help of the calculations. (C) 2004 American Institute of Physics.