mpirun.args: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/lib64/mvapich-psm/bin/mpirun.args - from package: mvapich-psm
/usr/lib64/mvapich/bin/mpirun.args - from package: mvapich
/usr/lib/mvapich/bin/mpirun.args - from package: mvapich

You may install the required package with command yum install {package}

Error in other languages:
mpirun.args: bevel nie gevind nie
mpirun.args: comandă negăsită
mpirun.args: comando não encontrado
mpirun.args: commande introuvable
mpirun.args: command not found
mpirun.args: käsku ei ole
mpirun.args: không tìm thấy lệnh
mpirun.args: komanda nerasta
mpirun.args: Kommando nicht gefunden.
mpirun.args: kommandot finns inte
mpirun.args: komut yok
mpirun.args: nie znaleziono polecenia
mpirun.args: níor aimsíodh an t-ordú
mpirun.args: no se encontró la orden
mpirun.args: no s'ha trobat l'ordre
mpirun.args: opdracht niet gevonden
mpirun.args: parancs nem található
mpirun.args: perintah tidak ditemukan
mpirun.args: príkaz nenájdený
mpirun.args: příkaz nenalezen
mpirun.args: команда не найдена
mpirun.args: командата не е открита
mpirun.args: 命令找不到
mpirun.args: コマンドが見つかりません