Particles disappearing

Hi all,

I am encountering a problem here where my particles are disappearing and not behaving normally.
I am simulating a closed-end cone that filled with 100 micrometer diameter particles.
I notice that when I bigger diameter particle (smallest I can do is 150 micrometer diameter), the simulation still works and doesn't behave strange. So the problem only occurs on diameter less than 150 micrometer.
Is there anybody that can help me with this?

I also attach the .avi file but can only upload it in .txt, you can change the extension.

Regards,
Bernard

Here is my simulation script:

#############Header for General commands#################

atom_style granular #Simulation of particles

boundary f f f #fixed boundaries -> particles will be deleted if leaving the simulation box

units cgs

communicate single vel yes #default

newton off #default

##############System variables###################

#Definition of boundaries
variable xmin equal -0.15
variable xmax equal 0.15

variable ymin equal -0.15
variable ymax equal 0.15

variable zmin equal -0.3
variable zmax equal 6

#Definition of the timestep

variable dt equal 1e-5 #timestep = 0.0001 second

##############Specific variables for current simulation##############

variable natoms equal 2 #1 -> particle #2->hopper and ground

####variable for material properties#### (DONE)

####Young Modulus####
variable youngmodulus1 equal 211e9 #Ba
variable youngmodulus2 equal 211e9 #Ba

####Poisson ratio####
variable poisson1 equal 0.3
variable poisson2 equal 0.3

####variable for contact properties####

####coefficient of restitution####
variable CoR11 equal 0.1 #0.64
variable CoR12 equal 0.1
variable CoR21 equal 0.1
variable CoR22 equal 0.1

####sliding friction coefficient####
variable sf11 equal 0.50
variable sf12 equal 0.50
variable sf21 equal 0.50
variable sf22 equal 0

####rolling friction coefficient####
variable rf11 equal 0.8
variable rf12 equal 0.8
variable rf21 equal 0.8
variable rf22 equal 0

####variable for cohesion####
variable ch11 equal 9
variable ch12 equal 9
variable ch21 equal 9
variable ch22 equal 0

####variable for particle####

#Number of particle radius
variable nradii equal 1 #4

variable radius1 equal 0.0050 #cm

variable frac1 equal 1

variable density equal 8 #g/cm³

####filling parameters####

variable filltime equal 0.25 #seconds

variable fillmass equal 0.05 #g

variable fillmassrate equal ${fillmass}/${filltime} #g/s

variable fillsteps equal ${filltime}/${dt} #Transform time to iteration steps

####settle time#### (DONE)

variable settletime equal 0.01 #second

variable settlesteps equal ${settletime}/${dt} #Transform time to iteration steps

###############Definition of simulationbox######################

region reg block ${xmin} ${xmax} ${ymin} ${ymax} ${zmin} ${zmax} units box

create_box 2 reg

neighbor 0.004 bin #default

neigh_modify delay 0 #default

hard_particles yes #cgs young modulus more than 1e10

##################Definition of the contact models#####################

pair_style gran model hertz tangential history cohesion sjkr rolling_friction epsd2 #contact model

pair_coeff * * #default

timestep ${dt}

fix integrator all nve/sphere #default

fix gravi all gravity 981 vector 0.0 0.0 -1.0 #gravity of 981 cm/s² in negative z direction

#####################Definition of Material properties#########################

fix m1 all property/global youngsModulus peratomtype ${youngmodulus1} ${youngmodulus2}

fix m2 all property/global poissonsRatio peratomtype ${poisson1} ${poisson2}

fix m3 all property/global coefficientRestitution peratomtypepair ${natoms} ${CoR11} ${CoR12} ${CoR21} ${CoR22}

fix m4 all property/global coefficientFriction peratomtypepair ${natoms} ${sf11} ${sf12} ${sf21} ${sf22}

fix m5 all property/global coefficientRollingFriction peratomtypepair ${natoms} ${rf11} ${rf12} ${rf21} ${rf22}

fix m6 all property/global cohesionEnergyDensity peratomtypepair ${natoms} ${ch11} ${ch12} ${ch21} ${ch22}

#################Generation and Loading of the Geometry .stl########################

fix ground all mesh/surface file Ground360H.stl type 2 scale 0.1 curvature 1e-5 #move0.135 #load mesh from STL file. Type 2 for geometry. Scale down to transform mm to cm
fix inlet all mesh/surface file In360H.stl type 2 scale 0.1 curvature 1e-5
fix nozzle all mesh/surface file Noz360H_60C.stl type 2 scale 0.1 curvature 1e-5

fix walls all wall/gran model hertz tangential history cohesion sjkr rolling_friction epsd2 mesh n_meshes 2 meshes ground nozzle

#################Generation and Insertion of the particles###################

fix pts1 all particletemplate/sphere 10007 atom_type 1 density constant ${density} radius constant ${radius1}

fix pdd1 all particledistribution/discrete 32452867 ${nradii} pts1 ${frac1} #pts2 ${frac2} pts3 ${frac3} pts4 ${frac4}

fix ins_mesh all mesh/surface/planar file In360H.stl type 1 scale 0.1

fix ins all insert/stream seed 86028157 distributiontemplate pdd1 &
mass ${fillmass} massrate ${fillmassrate} overlapcheck yes all_in yes vel constant 0 0 -30 &
insertion_face ins_mesh extrude_length 0.2

#############Dumping of the data for post-processing to visualize###############

shell mkdir post0

#Definition of the dumptime

variable dumptime equal 0.0025 # Every 0.0001 s 1 image

variable dumpstep equal ${dumptime}/${dt} #Transform to iteration steps

dump d0 all custom ${dumpstep} post0/dump*.particles id type x y z ix iy iz vx vy vz fx fy fz omegax omegay omegaz radius
dump dmpground all mesh/stl ${dumpstep} post0/Ground*.stl ground
dump dmpnozzle all mesh/stl ${dumpstep} post0/Nozzle*.stl nozzle

#########RUN the simulation filling#####################

run ${fillsteps}

unfix ins

##########RUN the simulation settling##################

run ${settlesteps}