In this method, the energy was minimized by repeating minimization along the direction of the force. The first derivative of the potential energy surface was used with respect to the Cartesian coordinates. The method moves in the parallel direction to the net force by considering moving down the steepest slope of the interatomic forces on the potential energy surfaces. By adding an increment to the negative gradient of the potential energy ( ) or forces, the descent is accomplished (see Figure 3.3).
The method is commonly used in the initial step for relaxing the poorly refined structure either resolved from the crystallography or model building since it reasonably converges at the initial step and requires minimal computing time. However, the progress becomes slow when approaching the minimum. This leads to another minimization method known as conjugate gradient to be used.