|From:||Ray Shan <rshan@...1795...>|
|Date:||Tue, 29 Aug 2017 22:27:15 +0000|
Your charges did not converge so atoms probably ended up with spurious charge values, causing Coulomb potential to misbehave.
1. Start with more meaningful initial charges, i.e., charges that are close to equilibrium charges or just some fractional values instead of zeros would help a lot.
2. Check your QEq parameters in “bi2o3.parm” as they might not make sense.
I was trying to develop charges on a crystal by using Qeq. I found the ionization potential and electron affinity parameters to get the Mulliken electronegativity, which is used by Qeq. But it gave NaN on charges and those energies. The crystal structure is from the standard database. It seems there is something wrong blowing up the system. Can anyone know how to deal with it? I was using the same method successfully once before, but I have no idea why this time it is not working.
Here is the input.
#boundary p p p
pair_style buck/coul/long 12.0
kspace_style ewald 1.0e-6
pair_coeff 1 1 6452.86 0.5089 0.0000
pair_coeff 1 2 6048.95 0.5162 0.0000
pair_coeff 2 2 5670.33 0.5235 8.1163
neighbor 2.0 bin
neigh_modify delay 0 every 1 check yes
group type1 type 1
compute charge1 type1 property/atom q
compute q1 type1 reduce ave c_charge1
group type2 type 2
compute charge2 type2 property/atom q
compute q2 type2 reduce ave c_charge2
variable qtot equal count(type1)*c_q1+count(type2)*c_q2
thermo_style custom step pe c_q1 c_q2 v_qtot spcpu
velocity all create 300.0 1281937
fix 1 all nve
fix 2 all qeq/dynamic 1 10 1.0e-3 100 bi2o3.parm
Here is the error:
WARNING: Charges did not converge at step 0: nan (../fix_qeq_dynamic.cpp:165)
ERROR on proc 0: Non-numeric atom coords - simulation unstable (../domain.cpp:521)