[gmx-users] Coefficients for user-defined tabulated potentials (topol.top + table.xvg)

[David Waroquiers]

Hello !

I would like to have some information about how to set the coefficients
for tabulated potentials.

I'm using coulombtype ewald and vdwtype user so I have to define tables
for each pair of atoms (and/or one table all the rest of them) :
table.xvg
table_Si_O.xvg
table_Si_Si.xvg
table_O_O.xvg

I've created these tables but I dont understand how to set the C6 and
C12 coefficients : in the topology, the directive [ nonbond_params ] can
be used to define C6 and C12 coefficients but only for lennard jones and
buckingham potentials (I did'nt find how to set it for user tables in
the manual nor in the mailing list).

I've managed to run simulations by including C6 and C12 directly in the
tables and define atomtypes with C6 and C12 set to 1.0 so that applying
combination rule gives C6=1.0 and C12=1.0 for all pair of atoms but it
would be much more convenient if the coefficients were set explicitly in
the topology and not in the user tables.

Thanks in advance


-- 
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David Waroquiers, Phd Student
European Theoretical Spectroscopy Facility (ETSF)
Unité de Physico-Chimie et de Physique des Matériaux (PCPM)
Université Catholique de Louvain (UCL)
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Address :
Bâtiment Boltzmann
Place Croix du Sud, 1
1348 Louvain-la-Neuve, Belgique
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E-mail : david.waroquiers at uclouvain.be
Tel : + 32 (0)10 / 47 28 38
Fax : + 32 (0)10 / 47 34 52
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