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青春逍遥啊

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[求助] 计算石墨烯热导率平衡态，求助！已有2人参与

如题，我想用lammps计算石墨烯的平衡态热导率，我用ms建立16*16*1的石墨烯模型，边界条件如果是ppp，则运行没有问题，如果改为pps，则总是出现如下错误：
   cannot use neighbor bins -box size << cutoff (../neighbor.cpp:1737)
按照lammps error中的提示，显示

Cannot use neighbor bins - box size << cutoffToo many neighbor bins will be created. This typically happens when the simulation box is very small in some dimension, compared to the neighbor cutoff. Use the “nsq” style instead of “bin” style.

我尝试着将我的box设置大一点，从16*16*1改为50*50*1，可是错误依然存在。势函数采用的是tersoff势函数。

部分in文件如下：

units    metal
variable T equal 300       # in K
variable V equal vol       # in A^3
variable dt equal 0.0005    # in ps
variable p equal 100000    # correlation length
variable s equal 1    # sample interval
variable d equal $p*$s # dump interval

# convert from LAMMPS real units to SI # donot change this part

variable kB equal 1.3806504e-23 # [J/K] Boltzmann
variable eV2J equal 1.60217646e-19
variable A2m equal 1.0e-10
variable ps2s equal 1.0e-12
variable convert equal ${eV2J}*${eV2J}/${ps2s}/${A2m}

# setup problem

#dimension 3
#boundary    p p p
#lattice    fcc 5.376 orient x 1 0 0 orient y 0 1 0 orient z 0 0 1

#region    box block 0 4 0 4 0 4
#create_box 1 box
#create_atoms 1 box
#mass       1 39.948
#pair_style lj/cut 13.0
#pair_coeff * * 0.010325 3.405
#timestep    ${dt}
#thermo    $d

# for reading data file

# read structure from data file

dimension 3
boundary    p p s
read_data       data.graphite

#potential function

pair_style  tersoff
pair_coeff * * SiC.tersoff Si
timestep    ${dt}
thermo    $d

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1楼 2016-05-13 12:42:37

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brucefan

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15楼: Originally posted by 青春逍遥啊 at 2016-05-19 19:36:38
您说的文献不知道您现在是否还记得，我参考的一篇取得石墨烯厚度是1.42埃。您的意思是这个势函数是多体势，不适合在用lammps根据GK方程求热导率，那采用什么样的势函数会相对比较合适呢？如果用airebo势函数呢？或 ...

Yes, someone uses 1.42 Angatrom, but most people use 3.35 Angstrom. You should state the value you choose when reporting your data. This is just a choice and is not important.

Yes, Green-Kubo in lammps with many-body potentials (such as Tersoff, Stillinger-Weber, REBO, AIREBO, ect) is WRONG and should NOT be used. You can find details in my paper:

http://journals.aps.org/prb/abstract/10.1103/PhysRevB.92.094301

Using NEMD is OK, because the heat current is added externally. But NEMD is very time-consuming if you want to extrapolate to the infinite-size limit.