*3.5. Construction of 3- Dimensional Model*

The three-dimensional model is constructed for the 2- dimensional structure of HLH before and after modification, whose three-dimensional geometric optimization configuration is calculated by MM and MD of Forcite module in Materials Studio 8.0 software. The structure model of HLH before and after optimization is shown in Figures 11–13, and the energy change in the process of optimization is shown in Table 15.

(**a**) Initial 3-dimensional structure model (**b**) Optimized by MM and MD

**Figure 11.** 3-dimensional structure of HLH lignite model before and after geometric optimization.

**Figure 12.** 3-dimensional structure of HLH lignite model modified by microwave before and after geometric optimization.

(**a**) Initial 3-dimensional structure model (**b**) Optimized by MM and MD

**Figure 13.** 3-dimensional structure of HLH lignite model modified by ultrasound before and after geometric optimization.


**Table 15.** Energy comparison before and after HLH structural model optimization.

It can be seen from this that the total energy of the minimum energy structures of the three structures decreases sharply. Compared with other terms, the value of Van der Waals energy (EVan) in the non-bonding energy is the largest, which constitutes the most important part of the potential energy. Therefore, the decrease of the inter-molecular Van der Waals energy (EVan) is also the main factor that makes the HLH macromolecular structure model stable in space.
