excitingmpi_mpich: 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/excitingmpi_mpich - from package: exciting-mpich

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

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