Hi, all

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1

Recently, I am trying to simulate water on silica surface using TIP4P/ice model. But I come to the error “TIP4P hydrogen is missing” occasionally. What confuse me is this problem shows up after thousands of timestep, not at the very beginning of the simulation. The following is my input script. Any help will be gratful.

units real
boundary p p f
atom_style full
read_data water.data
#group definition--------------------------
group all type 1 2 3 4 5 6 # 1_O H2O, 2_H H2O; 3_O SiO2, 4_Si SiO2, 5_O Oh, 6_H Oh
group surf type 3 4 5
group OH type 6
group water type 1 2

bond definition--------------------------

bond_style harmonic
bond_coeff 1 450 0.9572
bond_coeff 2 596 0.968

angle definition------------------------

angle_style harmonic
angle_coeff 1 55 104.52
angle_coeff 2 22.1 120.0

pair_style definition-------------------

pair_style hybrid/overlay lj/cut/coul/long/tip4p 1 2 1 1 0.1577 6.5 lj/cut/coul/long 6.5

pair_coeff setting

water-water interaction

pair_coeff 1 1 lj/cut/coul/long/tip4p 0.21085 3.1668 # TIP4P-ice 1kcal=4.184 J1
pair_coeff 1 2 lj/cut/coul/long/tip4p 0.0 0.0
pair_coeff 2 2 lj/cut/coul/long/tip4p 0.0 0.0

pair_coeff 2 36 lj/cut/coul/long 0.0 0.0 # H2O–SiO2-oH coloumb force
pair_coeff 1 6 lj/cut/coul/long 0.0 0.0 # O_H2O H-OH
pair_coeff 36 6 lj/cut/coul/long 0.0 0.0 # SiO2 H-OH

pair_coeff 1 3 lj/cut/coul/long 0.1810 3.1662 # O_H2O–O_SiO2
pair_coeff 1 5 lj/cut/coul/long 0.1810 3.1662 # O_H2O–O_-OH
pair_coeff 1 4 lj/cut/coul/long 0.1452 3.5834 # O_H2O–Si_SiO2

SiO2-SiO2 interaction Bulk

pair_coeff 35 35 none

pppm setting

neigh_modify every 1 delay 0
kspace_style pppm/tip4p 1.0e-4 #Periodic boudary condtion is required
kspace_modify slab 3.0

velocity intialization--------------------

velocity all create 300 3322 dist gaussian

fix setting-------------------------------

2

Recently, I am trying to simulate water on silica surface using TIP4P/ice
model. But I come to the error "TIP4P hydrogen is missing" occasionally.
What confuse me is this problem shows up after thousands of timestep, not
at the very beginning of the simulation. The following is my input script.
Any help will be gratful.

​please visualize your trajectory and see if there are any "special things"
happening. one possibility is that your wall is too soft or that your water
silica interactions are not working and atoms get too close.​

​please also note that a LJ cutoff of 6.5 is *extremely* short and will
lead to significant discontinuities in your potential and bad energy
conservation. something of the order of 12 or 14​ is more appropriate these
days. furthermore there is no need to use a hybrid pair style (and why on
earth hybrid/overlay??). lj/cut/coul/long/tip4p works as lj/cut/coul/long
for all atoms that are not the TIP4P water atoms. please check the
documentation.

axel.