Possibility of observing third thermomechanical (TM) effect in uniform nematic liquid crystals (NLC) with
proper selection of boundary conditions on the cell walls is theoretically studied. Absorption of a light
wave induces the needed temperature gradient for the TM effect. The molecular director reorientation
due to third TM effect and the induced phase shift on the probe beam are calculated. The forth TM
coefficient can be measured directly by the method proposed in this work.