Simulation of water potential for the electronic structureof serine

First-principles, all-electron, textit{ab initio} calculationshave been performed to construct an equivalent water potentialfor the electronic structure of serine (Ser) in solution. Thecalculation is composed of three steps. The first step is to searchfor the configuration of the Ser + NH₂O system with a minimumenergy. The second step is to calculate the electronic structure ofSer with the water molecule potential via the self-consistentcluster-embedding method (SCCE), based on the result obtained in thefirst step. The last step is to calculate the electronic structureof Ser with the dipole potential after replacing the water moleculeswith dipoles. The results show that the occupied states of Ser areraised by about 0.017~Ry on average due to the effect of water. Thewater effect can be successfully simulated by using the dipole potential.The obtained equivalent potential can be applied directly to theelectronic structure calculation of protein in solution by using theSCCE method.