run_mopac7: 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 Debian possible default full paths are:

/usr/bin/run_mopac7 - from package: mopac7-bin

You may install the required package with command apt-get install {package}

Error in other languages:
run_mopac7: bevel nie gevind nie
run_mopac7: comandă negăsită
run_mopac7: comando não encontrado
run_mopac7: commande introuvable
run_mopac7: command not found
run_mopac7: käsku ei ole
run_mopac7: không tìm thấy lệnh
run_mopac7: komanda nerasta
run_mopac7: Kommando nicht gefunden.
run_mopac7: kommandot finns inte
run_mopac7: komut yok
run_mopac7: nie znaleziono polecenia
run_mopac7: níor aimsíodh an t-ordú
run_mopac7: no se encontró la orden
run_mopac7: no s'ha trobat l'ordre
run_mopac7: opdracht niet gevonden
run_mopac7: parancs nem található
run_mopac7: perintah tidak ditemukan
run_mopac7: príkaz nenájdený
run_mopac7: příkaz nenalezen
run_mopac7: команда не найдена
run_mopac7: командата не е открита
run_mopac7: 命令找不到
run_mopac7: コマンドが見つかりません