spectra_manipulation.x: 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/bin/spectra_manipulation.x - from package: quantum-espresso

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

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