Use of L-F approximation method in the solution of second order secular equation in molecular dynamics has been crtically examined in this report. It has been established that use of too many constraints lead to multiplicity of solutions. The solution of second order secular equation can be easily obtained without solving any quadratic equation giving symmetry force constants identical with those given by Peacock and Mullers method. The solution prescribed by the exponents of L-F approximation method is slightly different due to neglect of F2ijin forming the quadratic equation for the solution of second order secular equation.