wdec is used to evolve grids of DA-variable (DAV) star models adopting the element diffusion scheme with pure and screened Coulomb potentials. The core compositions are thermonuclear burning results derived from mesa. mesa yields composition profiles that the version of WDEC used in this work could not accommodate (most notably, the presence of helium in the core of the model). According to the theory of rotational splitting, Fu and colleagues identified six triplets for the DAV star HS 0507 + 0434B based on 206 h of photometric data. The grids of DAV star models are used to fit the six reliable m = 0 modes. When adopting the screened Coulomb potential, a best-fitting model of log(M-He/M-*)=-3.0, log(M-H/M-*)=-6.1, T-eff = 11 790 K, M-* = 0.625M(circle dot), log g = 8.066 and sigma(RMS) = 2.08 s was obtained. Compared with adopting the pure Coulomb potential, the value of sRMS is improved by 34 per cent. This study may provide a new method for research into mode-trapping properties.