I cross-linked the following polymer structures and simulated the resulting cell MD. I used CompassII force field to conduct 21-step NVT-NPT simulation (temperature 800K~300K, pressure 1bar~5Gpa,). Finally, we get the density at 1bar, which is not consistent with the experimental density. I tried to change the maximum temperature, force field, maximum pressure, time and other parameters, but could not improve the density.. Please give me some advice.

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