Help!!!!!!!

hi, i am tryig to simulate the deformation of a nanoribbon but i get strange
pressures values, this is my log file from a test file so, can anyone help me to
find what is wrong?

thanks!!

Log file
LAMMPS (30 Aug 2013)
  using 2 OpenMP thread(s) per MPI task

#----INITIALIZATION---------
dimension 2
units metal
atom_style atomic
boundary p p p

#----ATOM DEFINITION--------
read_data hexalam.txt
  orthogonal box = (-1 -1 -0.5) to (20.4856 19.7428 0.5)
  4 by 4 by 1 MPI processor grid
  55 atoms
  55 velocities
newton on

#----FORCE FIELDS-----------
pair_style edip
pair_coeff * * Si.edip Si

#----SETTINGS---------------

#COMPUTES REQUIRED
#compute csym all centro/atom 3
compute 2 all stress/atom
compute mytemp all temp
compute 11 all reduce sum c_2[1]
compute 12 all reduce sum c_2[2]
compute 13 all reduce sum c_2[3]
compute 14 all reduce sum c_2[4]

neighbor 0.3 bin
neigh_modify delay 10
thermo 100
velocity all create 300.0 16723 mom yes rot no
thermo_style custom step temp etotal press pxx pyy lx ly
shell mkdir dump
shell cd dump

#ENERGY EQUILIBRATION
reset_timestep 0
fix 1 all nve
fix 2 all temp/rescale 10 300.0 300.0 1.0 0.5
dump 1 all custom 5000 dump.equilibrate.* id type x y

run 1000
Memory usage per processor = 3.28599 Mbytes
Step Temp TotEng Press Pxx Pyy Lx Ly
       0 300 -150.55328 -1178972.1 -1179893.9 -1178050.3
21.485572 20.742786
     100 454.76475 -184.98361 -779157.11 -526826.98 -1031487.2
21.485572 20.742786
     200 371.81447 -190.22124 -658633.6 -426057.42 -891209.78
21.485572 20.742786
     300 367.57188 -196.21994 -538142.44 -356058.42 -720226.45
21.485572 20.742786
     400 359.8245 -198.49801 -445265.34 -271168.85 -619361.83
21.485572 20.742786
     500 315.31615 -199.29182 -444852.81 -266653.89 -623051.72
21.485572 20.742786
     600 276.70558 -199.00286 -460567.24 -295228.16 -625906.33
21.485572 20.742786
     700 300.77186 -199.43328 -469347.56 -318719.43 -619975.7
21.485572 20.742786
     800 294.20894 -199.37326 -471518.01 -288042.83 -654993.2
21.485572 20.742786
     900 282.99331 -199.26854 -471351.83 -288059.95 -654643.72
21.485572 20.742786
    1000 286.77407 -199.47323 -470425.54 -293759.24 -647091.84
21.485572 20.742786
Loop time of 0.337814 on 32 procs (16 MPI x 2 OpenMP) for 1000 steps with 55 atoms

Pair time (\) = 0\.00489472 \(1\.44894\) Neigh time \() = 0.000400871 (0.118666)
Comm time (\) = 0\.247852 \(73\.3693\) Outpt time \() = 0.00704043 (2.08411)
Other time (%) = 0.077626 (22.9789)

Nlocal: 3.4375 ave 5 max 2 min
Histogram: 2 0 0 7 0 0 5 0 0 2
Nghost: 14.25 ave 18 max 11 min
Histogram: 2 3 1 0 2 3 0 2 2 1
Neighs: 0 ave 0 max 0 min
Histogram: 16 0 0 0 0 0 0 0 0 0
FullNghs: 11.625 ave 16 max 7 min
Histogram: 2 0 2 2 0 6 0 1 0 3

Total # of neighbors = 186
Ave neighs/atom = 3.38182
Neighbor list builds = 65
Dangerous builds = 8
unfix 1
unfix 2

undump 1
shell cd ..
shell mkdir deform

#STORING INITIAL LENGHT
variable tmp equal "lx"
variable LO equal \{tmp\}\-2\.0 variable LO equal 21\.485572000000001225\-2\.0 print "Initial Length, LO: {LO}"
Initial Length, LO: 19.485572000000001225

#DEFORMATION
reset_timestep 0
variable srate equal 0.0005
variable strain equal "v_srate/1e12"
fix 1 all deform 1 x erate ${strain} units box
fix 1 all deform 1 x erate 5.0000000000000003885e-16 units box
fix 2 all nvt temp 300.0 300.0 100.0

#OUTPUT STRAIN AND STRESS INFO FILE
#for units metal, pressure is in [bars] = 100 [kPa] = 1/10000 [GPa]
#p2, p3, p4
variable strain equal "(lx - v_LO)/v_LO"
variable p1 equal "v_strain"
variable p2 equal "-pxx/10000"
variable p3 equal "-pyy/10000"
variable p4 equal "-pxy/10000"
variable p5 equal "lx"
variable p6 equal "ly"
variable p7 equal "temp"
variable p8 equal "pe"
variable p9 equal "ke"
variable fm equal "(v_p2+v_p3)/2"

dump 2 all custom 1000 dump.defo.* id type x y c_2[1] c_2[2] c_2[3] c_2[4]
c_2[5] c_2[6]

#DISPLAY THERMO
#thermo 100
#thermo_style custom step v_p1 v_p2 v_p3 v_p4 v_p5 v_p6 v_p7 v_p8 v_p9

fix ABC all print 100 "\{p1\} {p2} \{p3\} {p4} \{p5\} {p6} \{p7\} {p8} \{p9\} {fm}" file Si001.defo.txt

run 1000
Memory usage per processor = 4.20188 Mbytes
Step Temp TotEng Press Pxx Pyy Lx Ly
       0 286.77407 -199.47323 -470425.54 -293759.24 -647091.84
21.485572 20.742786
0.10264004567071471907 27.943037273181463576 64.446046390229426493
-1.3754919968875394254 21.485572000000001225 20.742785999999998836
328.10815048619787149 -201.00047854610028253 1.5268070558709994078
46.194541831705443258
     100 328.10815 -199.47367 -461945.42 -279430.37 -644460.46
21.485572 20.742786
0.10264004567071471907 28.210074682147567415 66.052499607067659326
-2.426012862081867727 21.485572000000001225 20.742785999999998836
239.47082111583648611 -200.58755680817270672 1.114345190185275225
47.131287144607611594
     200 239.47082 -199.47321 -471312.87 -282100.75 -660525
21.485572 20.742786
0.10264004567071489948 27.196133468896103835 63.446611577152772554
-1.2108948115600974837 21.485572000000004778 20.742785999999998836
291.81161288360334538 -200.8315156325135149 1.3579060101846638364
45.321372523024436418
     300 291.81161 -199.47361 -453213.73 -271961.33 -634466.12
21.485572 20.742786
0.1026400456707150799 25.650473175490429156 66.119779306082236303
-3.509769978551324332 21.48557200000000833 20.742785999999998836
309.14099189380715416 -200.91189702526673955 1.4385459397549442695
45.885126240786334506
     400 309.14099 -199.47335 -458851.26 -256504.73 -661197.79
21.485572 20.742786
0.1026400456707150799 25.495912475617746651 63.407127243951393325
-2.9857690461701142937 21.48557200000000833 20.742785999999998836
364.15519720635916201 -201.16849160677296027 1.6945471293623131093
44.451519859784568212
     500 364.1552 -199.47394 -444515.2 -254959.12 -634071.27
21.485572 20.742786
0.1026400456707150799 28.470190530422271991 62.538356843626672799
-4.353759666274315876 21.48557200000000833 20.742785999999998836
280.96333052181967105 -200.7810567392822918 1.3074249903456003352
45.504273687024472395
     600 280.96333 -199.47363 -455042.74 -284701.91 -625383.57
21.485572 20.742786
0.1026400456707150799 27.482233051655239109 63.555447571067183787
-4.6846340559377361856 21.48557200000000833 20.742785999999998836
281.68630309012496582 -200.78426494860235607 1.3107892457499661365
45.518840311361209672
     700 281.6863 -199.47348 -455188.4 -274822.33 -635554.48
21.485572 20.742786
0.10264004567071526031 28.251772740245897353 62.647550785240774474
-4.7298353114657150087 21.485572000000011883 20.742785999999998836
265.03718004358626104 -200.70671692269689856 1.2333147956217025421
45.449661762743332361
     800 265.03718 -199.4734 -454496.62 -282517.73 -626475.51
21.485572 20.742786
0.10264004567071526031 25.405779890738294569 66.053375392689801515
-2.6640962968117127829 21.485572000000011883 20.742785999999998836
334.36368861327730428 -201.02930991478183387 1.5559163594239346917
45.729577641714044489
     900 334.36369 -199.47339 -457295.78 -254057.8 -660533.75
21.485572 20.742786
0.10264004567071526031 27.609525812201567874 66.396691372191625646
-0.64279726158244232526 21.485572000000011883 20.742785999999998836
249.85087679946383332 -200.63577684797513712 1.1626473802851300388
47.00310859219659676
    1000 249.85088 -199.47313 -470031.09 -276095.26 -663966.91
21.485572 20.742786
Loop time of 0.470429 on 32 procs (16 MPI x 2 OpenMP) for 1000 steps with 55 atoms

Pair time (\) = 0\.00504296 \(1\.07199\) Neigh time \() = 0.00024204 (0.0514508)
Comm time (\) = 0\.247989 \(52\.7155\) Outpt time \() = 0.0113945 (2.42214)
Other time (%) = 0.205761 (43.7389)

Nlocal: 3.4375 ave 5 max 2 min
Histogram: 3 0 0 6 0 0 4 0 0 3
Nghost: 13.75 ave 18 max 10 min
Histogram: 1 2 4 0 0 2 3 2 1 1
Neighs: 0 ave 0 max 0 min
Histogram: 16 0 0 0 0 0 0 0 0 0
FullNghs: 11.75 ave 16 max 6 min
Histogram: 2 0 1 2 1 0 2 3 1 4

Total # of neighbors = 188
Ave neighs/atom = 3.41818
Neighbor list builds = 51
Dangerous builds = 0

The pressure is not the only strange thing about this script. For example:

fix 1 all deform 1 x erate 5.0000000000000003885e-16 units box

Are you complaining about the large negative values of pressure? I
can't say that these are wrong, because you did not tell us anything
about the input geometry. Also, because you are running a 2d
simulation, the pressure is defined as virial/area, not virial/volume.
Hence the units of pressure are not the normal metal pressure units
(bar).

I suggest you take a step back and first figure out how to match some
know properties of the EDIP potential for silicon.

Aidan