Hi gmx-users, I want to calcualted the the vaporation enthalpy of benzaldehyde I think that the the vaporation enthalpy is the sum of non-bond interacion among the benzaldehyde molecule. So I made a NPT system simulation including 512 benzaldehyde molecule. The following is the intermolecule nonbond interaction using the g_energy.
LJ-(SR)= -21128.7 Kj/mol LJ-(LR)= -889.855 Kj/mol Coulomb-(SR)= -3884.6 Kj/mol Coul.-recip = -2261.51 Kj/mol the sum of non-bond interaction = LJ-(SR) + LJ-(LR) + Coulomb-(SR) + Coul.-recip = 28164.665 Kj/mol But the experimental value of he vaporation enthalpy = 50.3 Kj/mol I have no ideal that why they have so much different. Now I don't know how to solve it. Any suggestion will be appreciated. This following is my md.mdp file. title = fws cpp = /usr/bin/cpp constraints = all-bonds integrator = md dt = 0.002 ; ps ! nsteps = 500000 ; total 1ns nstcomm = 1 nstxout = 500 nstvout = 0 nstfout = 0 nstlist = 10 ns_type = grid rlist = 1.0 coulombtype = PME rcoulomb = 1.0 vdwtype = cut-off rvdw = 1.4 fourierspacing = 0.12 fourier_nx = 0 fourier_ny = 0 fourier_nz = 0 pme_order = 6 ewald_rtol = 1e-5 optimize_fft = yes ; Berendsen temperature coupling is on in three groups Tcoupl = berendsen tau_t = 0.1 tc_grps = system ref_t = 298.15 ; Pressure coupling is on Pcoupl = berendsen tau_p = 2.0 compressibility = 4.6e-5 ref_p = 1.0 ; Generate velocites is on at 323.15 K. gen_vel = yes gen_temp = 298.15 gen_seed = 173529 Jinyao Wang wan...@ciac.jl.cn 2009-10-23
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