SCO is also influenced by the application of pressure, which changes the population of the HS and LS states.  Upon application of pressure, a conversion from the HS state to the LS state and a shift from T, (the temperature at which half of the complex is in a LS state), to higher temperatures will occur.  This effect results from an increase in the zero point energy difference, ΔE°, caused by an increase in the relative vertical displacement of the potential wells and a decrease in the activation energy, ΔW°, which favors the LS state. The complex Fe(phen)(SCN) exhibits this effect. At high pressures the LS state predominates and the transition temperature increases. At high pressures the compound is almost entirely transformed to the LS state at room temperature.  As a result of the application of pressure on the Fe(phen)(SCN) compound, the bond lengths are affected.  The difference in M-L bond lengths in both HS and LS states changes the entropy of the system. The change in spin transition temperature, T and pressure obeys the Clausius-Clapeyron relationship:
The increase in pressure will decrease the volume of the unit cell of the Fe(phen)(SCN) and increase the T of the system. A linear relationship between T and pressure for Fe(phen)(SCN), where the slope of the line is .