turbo_davidson.x_mpich: command not found

Have You tried accessing the binary with the full path?

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

[root@server ~]# echo $PATH

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/turbo_davidson.x_mpich - from package: quantum-espresso-mpich

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