This is the basic form of the Verlet algorithm. Because Newton’s equation is being integrated, acceleration, a(t), is just the force divided by the mass. As one can see the truncation error of the algorithm when evolving the system by t is of the order of four, event if third derivatives do not appear explicitly. This algorithm is at the same time simple to implement, accurate and stable, explaining its large popularity among molecular dynamics simulations.
The advantages of the Verlet algorithm are, i) it is straightforward, and ii) the storage requirements are modest. The disadvantage is that the algorithm is of moderate precision. A problem with this version of the Verlet algorithm is that velocities are not directly generated. While they are not need for the time evolution, their knowledge is sometimes necessary. Moreover, they are required to compute the kinetic energy K, whose estimate is necessary to test the conservation of the total energy E=K+V. This is one of the most importance tests to verify that a MD simulation is proceeding correctly. One could compute the velocities from the position using