计算机符号fix,请问命令行中的＆符号是什么意思！

符号fix,请问命令行中的＆符号是什么意思！"/>

计算机符号fix,请问命令行中的＆符号是什么意思！

手册中的源码：

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atom_style atomic

units real

variable kB equal 1.3806504e?23 # [J/K] Boltzmann

variable kCal2J equal 4186.0/6.02214e23

variable T equal 70

variable V equal vol

variable dt equal 4.0

variable p equal 200 # correlation length

variable s equal 10 # sample interval

variable d equal $p*$s # dump interval

#==============================================================

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 * * 0.2381 3.405

timestep ${dt}

thermo $d

#=============equilibration and thermalization================

velocity all create $T 102486 mom yes rot yes dist gaussian

fix NVT all nvt temp $T $T 10 drag 0.2

run 1000

#=====================flux calculation========================

reset_timestep 0

compute myKE all ke/atom

compute myPE all pe/atom

compute myStress all stress/atom virial

compute flux all heat/flux myKE myPE myStress

variable Jx equal c_flux[1]/vol

variable Jy equal c_flux[2]/vol

variable Jz equal c_flux[3]/vol

#fix JJ all ave/correlate $s $p $d & c_flux[1] c_flux[2] c_flux[3] type auto file J0Jt

fix JJ all ave/correlate $s $p $d c_flux[1] c_flux[2] c_flux[3] type auto file J0J.correlate

print "Wrong sentence here: Code 02"

##variable scale equal ${kCal2J}*${kCal2J}/${kB}/$T/$T/$V*$s*${dt}*1.0e25

variable scale equal "(${kCal2J}^2*$s*${dt}*1.0e25)/(${kB}*$T^2*$V)"

print "Wrong sentence here: Code 01"

variable k11 equal trap(f_JJ[4])*v_scale

print "Wrong sentence here: Code 04"

variable k22 equal trap(f_JJ[5])*v_scale

print "Wrong sentence here: Code 05"

variable k33 equal trap(f_JJ[2])*v_scale

print "Wrong sentence here: Code 03"

thermo_style custom step temp v_Jx v_Jy v_Jz #v_k11 v_k22 v_k33

print "Wrong sentence here: Code 06"

variable k equal (v_k11v_k22v_k33)/3.0

print "Wrong sentence here: Code 06"

print"average conductivity:$k [W/mK]"

run 10000

======================================================

报错信息：

Wrong sentence here: Code 02

Wrong sentence here: Code 01

Wrong sentence here: Code 04

Wrong sentence here: Code 05

Wrong sentence here: Code 03

Wrong sentence here: Code 06

Wrong sentence here: Code 06

ERROR: Invalid syntax in variable formula

好像是最后一句错误，但是错在哪里呢？ 郁闷！