scotch_dgtst: 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/mpich/bin/scotch_dgtst - from package: ptscotch-mpich
/usr/lib/mpich/bin/scotch_dgtst - from package: ptscotch-mpich
/usr/lib64/openmpi/bin/scotch_dgtst - from package: ptscotch-openmpi
/usr/lib/openmpi/bin/scotch_dgtst - from package: ptscotch-openmpi

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

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