An explanation of some phases of the organic insulator (TMTTF)(2)PF6 as a f
unction of temperature, magnetic field, and pressure is given. It is shown
that the problem can be mapped onto the (2 + 1)-dimensional nonlinear sigma
model. The physics is described in terms of the coupling constant of this
model, which encodes the one-dimensional two-body interactions and phonon e
ffects. A phase diagram is proposed, including a possible quantum critical
fixed point. [S0163-1829(99)01007-3].