请问下面的程序的错误怎样改啊，好急！！！！

lchylinchy

fini
/clear
/prep7
et,1,solid90
et,2,PLANE42
mp,kxx,1,0.21              !定义硅的导热系数
mp,dens,1,2230
k,1,0,0
k,2,1.5e-3,0
k,3,1.5e-3,0.04e-3
k,4,0,0.04e-3              !定义硅片的密度
l,1,2
l,2,3
l,3,4
l,4,1
al,1,2,3,4
lsel,s,,,1,3,2
lesize,all,,,100
lsel,s,,,2,4,2
lesize,all,,,4
type,2
amesh,all
!通过拉伸生成体单元
type,1
extopt,ESIZE,20     !指定拉伸方向划分数为3
extopt,ACLEAR,1    !拉伸完毕后，清除面单元
vext,all,,,,,0.2e-3   !z方向拉伸0.3e-3
fini
/solu

!施加一个直径为150μm的激光均匀热流密度
nsel,s,loc,x,0.6e-3,0.8e-3
nsel,r,loc,y,0.04e-3
nsel,r,loc,z,0.025e-3,0.175e-3
sf,all,hflux, 88108                   !施加均匀热流密度
alls
solv
fini


出现的错误提示是： Large negative pivot value ( -6.427497762E-18 ) in Eqn.system.  May be  
because of a bad temperature-dependent material property used in the   
model.