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feifanmg

新虫 (初入文坛)

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虫号: 5589510
注册: 2017-02-16
专业: 高分子科学

[求助] LAMMPS模拟均聚物拉伸，采用dpd、srp、msrp方法得到的应力应变图都是趋近0，求指导已有1人参与

链长40，分子数3000，dpd方法的in文件
variable simname index nc10_c11000
units          lj
atom_style    full
boundary p p p

special_bonds lj/coul 1 1 1
newton on on

# save an extra atom type for bond particles
read_data data.chain

neighbor       2.0 bin
neigh_modify every 10 check yes

bond_style    harmonic
bond_coeff    * 225.0 0.85

comm_modify vel yes

# must use pair hybrid, since srp bond particles
# do not interact with other atoms types
pair_style    dpd 1.0 1.0 373692
pair_coeff    1 1 60.0 4.5 1.0
thermo 1000
thermo_style custom step temp pe  press atoms  lx ly lz
dump             1 all custom 10000 dump1.lammpstrj id type x y z
fix  1 all nve
timestep       0.01

run       200000

unfix 1
#####################################################
# Uniaxial Tensile Deformation
run 0
variable tmp equal "lx"
variable L0 equal ${tmp}
variable strain equal "(lx - v_L0)/v_L0"
variable p1 equal "v_strain"
variable p2 equal "-pxx/10000*1.01325"
variable p3 equal "-pyy/10000*1.01325"
variable p4 equal "-pzz/10000*1.01325"
variable p5 equal "lx"
variable p6 equal "ly"
variable p7 equal "lz"
variable p8 equal "temp"
fix 1 all npt temp 1 1 1 y 0 0 1000 z 0 0 1000 drag 2
fix 2 all deform 1 x erate 1e-5 units box remap x
fix def1 all print 1000 "${p1} ${p2} ${p3} ${p4} ${p5} ${p6} ${p7} ${p8}" file ${simname}.def1.txt screen no
dump             2 all custom 10000 dump2.lammpstrj id type x y z
thermo_style custom step temp pxx pyy pzz lx ly lz
thermo       1000
timestep 0.01
reset_timestep 0
run 500000
unfix 2
unfix def1
------------------------------
srp方法的in文件如下
variable simname index nc10_c11000
units          lj
atom_style    full
boundary p p p

special_bonds lj/coul 1 1 1
newton on on

# save an extra atom type for bond particles
read_data data.chain

neighbor       2.0 bin
neigh_modify every 10 check yes

bond_style    harmonic
bond_coeff    * 225.0 0.85

comm_modify vel yes

# must use pair hybrid, since srp bond particles
# do not interact with other atoms types
pair_style    hybrid dpd 1.0 1.0 373692 srp 0.8 1 mid
pair_coeff    1 1 dpd 60.0 4.5 1.0
pair_coeff    1 2 none
pair_coeff    2 2 srp 100.0

# auto normalization of thermo quantites is turned off by pair srp
# just divide by natoms
variable       natoms equal count(all)
variable       nPotEng equal c_thermo_pe/v_natoms

thermo 1000
thermo_style custom step temp pe v_nPotEng press atoms v_natoms lx ly lz
dump             1 all custom 10000 dump1.lammpstrj id type x y z
fix  1 all nve
timestep       0.01

run       200000

unfix 1
#####################################################
# Uniaxial Tensile Deformation
run 0
variable tmp equal "lx"
variable L0 equal ${tmp}
variable strain equal "(lx - v_L0)/v_L0"
variable p1 equal "v_strain"
variable p2 equal "-pxx/10000*1.01325"
variable p3 equal "-pyy/10000*1.01325"
variable p4 equal "-pzz/10000*1.01325"
variable p5 equal "lx"
variable p6 equal "ly"
variable p7 equal "lz"
variable p8 equal "temp"
fix 1 all npt temp 1 1 1 y 0 0 1000 z 0 0 1000 drag 2
fix 2 all deform 1 x erate 1e-5 units box remap x
fix def1 all print 1000 "${p1} ${p2} ${p3} ${p4} ${p5} ${p6} ${p7} ${p8}" file ${simname}.def1.txt screen no
dump             2 all custom 10000 dump2.lammpstrj id type x y z
thermo_style custom step temp pxx pyy pzz v_nPotEng v_natoms lx ly lz
thermo       1000
timestep 0.01
reset_timestep 0
run 500000
unfix 2
unfix def1

40-dpd.jpg