Using the tensor LEED approach, we investigate the surface geometries of clean Si(100)-2x1 surface using initial guessed structures from slab and cluster model calculations. The theoretical LEED-IV curves generated were compared to the experimental LEED-IV curves using the Pendry R-factor (RPE). The RPE is known to be sensitive to the structural information. Results from the LEED-IV experiment together with the structural information obtained from the LEED-IV computations based on the different models are compared. Based on the fact that LEED-IV computations are capable of giving accurate structural results to the order of 0.1 Å and have also been known to solve surface structures accurately, our results are used to demonstrate the potential of LEED to be used in a non-traditional way to test different models.