Note that we show the one-dimensional Gauss (f (x)=Aexp{-(x -x 1 ) 2 /2σ 2 }) fitting for simplicity. Since a = ln A -x 2 {ln ρ -(a + bx + cx 2 )} 2 ) cannot be used for calculating a center. This is because the ordinal Gauss fitting is too sensitive for the noise of ρ(x) that appears in solving equation (2). On the other hand, the effect of noise is reduced in equation ( ) by weighting an error function with ρ(x). Therefore, employing Guo's fitting is the key to this phase-field simulation. Repeating the above procedure, the time development of an atom is calculated.