A Multi-Phase Transport Model (AMPT) has been extensively used to understand the physics behind the experimental observation. Like other models, the outcome of the AMPT model depends on the initial parameters. Therefore, one needs to choose suitable initial parameters before using the model. Lund string fragmentation function has been used to create quark-antiquarks pairs in the AMPT model. The Lund string fragmentation parameters determine the yields and transverse momentum (pT) spectra of particles produced in nucleus-nucleus collisions. The values of Lund string fragmentation parameters were determined by fitting the charged particle yield and pT spectra measured in the experiment. In this paper, using ϕ meson spectra measured at RHIC, we have obtained new sets of Lund parameters for Au+Au collisions at sNN = 11.5 GeV. We have found that using the same set of parameters, we can explain ϕ-meson yield at sNN = 39 and 200 GeV, however, we need a different set of parameters for sNN = 11.5 GeV. We have also predicted invariant yield of π, K and ϕ mesons as a function of pT in U+U collisions at sNN = 196 GeV to be measured by STAR experiment.