  The interaction of two screw dislocations in smectic-A liquid crystals is treated using an anharmonic correction to the elastic energy density. In the present contribution the elastic energy and the force between two screw dislocations is evaluated and discussed. For screw dislocations with both parallel and opposite Burgers vectors there is an attraction of dislocations for their small separations while for greater separations there is a repulsion. It can be explained by dominating terms in interaction energy which do not depend on signs of dislocations. In this way, the interaction energy of screw dislocations in smectic A liquid crystal within an anharmonic approximation differs with respect to the case of screw dislocations in solids. 
Screw dislocation interaction in smectic-A liquid crystals in an   anharmonic approximation