Dear all I am trying to calculate the binding energy for DNA adsorption on 2D sheets.I have done calculation by including vdW correction and simple PBE calculation with Ultrasoft pseudopotential. While studying the adsorption of the four nitrogen bases on the 2D surface I have observed that the binding energy for the cytosine adsorption on surface is coming out to be very different (almost three times larger) from what is expected when I include the vdW correction (vdw_corr = 'DFT-D') in to the calculations. Whereas, when I do only with PBE (no vdW correction) all the four bases gives expected correct energies.The parameters which has been included for vdW correction are as follows &SYSTEM ibrav = 0, celldm(1)= 1.89 , nat = 88, ntyp = 5, vdw_corr = 'DFT-D', london = .TRUE., ecutwfc = 50 , ecutrho = 500 , occupations = 'smearing' , smearing = 'gaussian' , degauss = 0.020 / &ELECTRONS electron_maxstep = 500 , conv_thr = 1.0d-5 , mixing_mode = 'plain' , mixing_beta = 0.7 , diagonalization = 'david' , / Please help me with this unexpected value of the binding energy value for the cytosine? Any kind of help would be appreciated.
Thank you Amita Sihag Research Student, Dept. of Chemistry Indian Institute of Technology Gandhinagar Gujrat (India)
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