Using the Lee code version (RADPFV5.15de), we carried out a series of numerical ‎experiments to find the parameters for the plasma focus and the soft X-ray yield for each of ‎nitrogen gas (molecular) and neon gas (atomic) within an appropriate temperature range for ‎PF400 dense plasma focus device. The results showed that the highest value of the soft X-ray ‎yield in neon was 0.148 J at 3.2 Torr pressure, while for nitrogen it was 0.0634 J at 4.4 Torr. This is ‎because of the higher atomic number and effective charge of neon as compared to nitrogen.