Dear Esteemed Colleagues,
I encountered the following error while simulating the FeCrAlCTi system using LAMMPS:
ERROR: Non-numeric pressure - simulation unstable. After consulting various resources, I have not found a solution. This error did not occur when I used the same IN file to calculate other atoms. When I switched to the Tersoff potential to describe Ti-C-Al, the error disappeared and the simulation ran, but the results were unsatisfactory. Based on previous literature, my system should use the MEAM potential mentioned in the error message. I kindly request your assistance in reviewing this issue and look forward to your insights and solutions.
Attached is my log file. Thank you for taking time out of your busy schedules to respond—this will be immensely helpful. Wishing everyone smooth progress in their research endeavors.
2025-12-10-1.log (4.8 KB)
in.FeCrAl (2.4 KB)
Hello,
Its difficult to help you without all the details, but your use of hybrid is clearly a possible origin for the error.
Also, please consider replacing the snapshots with an actual copy of your input, which you can properly format using the “preformatted text” option.
Simon
Thank you very much for your reply.
As a new user, I am unable to upload files. Below is my LAMMPS script for your review. Once again, thank you for your assistance. Wishing you good health and success in your research endeavors.
log 2025-12-10-1.log
units metal
boundary p p p
atom_style atomic
timestep 0.001
neighbor 2.0 bin
neigh_modify delay 10 every 10 check yes
read_data FeCrAlCTi.data
#-------
mass 1 55.845 #Fe
mass 2 51.996 #Cr
mass 3 26.981 #Al
mass 4 12 #C
mass 5 47.867 #Ti
pair_style hybrid eam/fs meam lj/cut 10.0
pair_coeff * * eam/fs FeCrAl.eam.fs Fe Cr Al NULL NULL
pair_coeff * * meam library.meam Ti C TiC.meam NULL NULL NULL C Ti
pair_coeff 1 4 lj/cut 0.0356 2.8092 #Fe-C
pair_coeff 1 5 lj/cut 0.1177 2.1318 #Fe-Ti
pair_coeff 2 5 lj/cut 0.1149 2.1387 #Cr-Ti
pair_coeff 2 4 lj/cut 0.0347 2.8182 #Cr-C
pair_coeff 3 4 lj/cut 0.0307 2.9846 #Al-C
pair_coeff 3 5 lj/cut 0.1016 2.2649 #Ti-Al
group Fe type 1
group C type 4
group Ti type 5
compute pe all pe/atom
compute ke all ke/atom
thermo 10000
thermo_style custom step temp etotal pe ke lx ly lz press pxx pyy pzz nbuild
write_data FeCrAlTiN.xyz
compute 1 C msd com yes
variable msdx1 equal c_1[1]
variable msdy1 equal c_1[2]
variable msdz1 equal c_1[3]
variable msd1 equal c_1[4]
variable istep equal step
fix 1 all print 500 “{istep} {msdx1} {msdy1} {msdz1} ${msd1}” screen no file Cmsd.dat
compute 2 Ti msd com yes
variable msdx2 equal c_2[1]
variable msdy2 equal c_2[2]
variable msdz2 equal c_2[3]
variable msd2 equal c_2[4]
variable istep equal step
fix 2 all print 500 “{istep} {msdx2} {msdy2} {msdz2} ${msd2}” screen no file Timsd.dat
velocity all create 300 686316
dump 2 all custom 500 FeCrAlshengwen.xyz id type element mass x y z fx fy fz vx vy vz c_pe c_ke
fix 3 all npt temp 300.0 1873.0 0.1 iso 0 0 1
dump_modify 2 element Fe Cr Al C Ti
run 100000
unfix 3
undump 2
dump 3 all custom 10000 dump.FeCrAlbaowen id type element mass x y z fx fy fz vx vy vz c_pe c_ke
fix 4 all nvt temp 1873.0 1873.0 0.1
dump_modify 3 element Fe Cr Al C Ti
run 10000000
unfix 4
undump 3
dump 4 all custom 10000 dump.FeCrAljiangwen id type element mass x y z fx fy fz vx vy vz c_pe c_ke
fix 5 all npt temp 1873.0 300.0 0.1 iso 0 0 1
dump_modify 4 element Fe Cr Al C Ti
run 100000
unfix 5
undump 4
write_data FeCrAlTiC-1873K.data
You are right, but you should still be able to format your input. Also, you can “edit” existing post instead of deleting / recreating them.
Thank you especially for your guidance. As this is my first time posting, I’m still learning the ropes. Please bear with me as I work to improve my posting and replying practices. Once again, thank you, and I look forward to receiving more guidance from you.
You can start your learning by carefully reading and following the guidelines in this post: Please Read This First: Guidelines and Suggestions for posting LAMMPS questions
Thank you very much for your advice. I will carefully read and follow the guidelines: Guidelines and Suggestions for posting LAMMPS questions. I will be more compliant in my future posts.