why total energy of a two-probe system is positive in 13.8.1 but negative in 08

[njuxyh]

Hi all

i have a two-probe system, in the past, i calculate its total potential energy in 2008 version, the following is
 ----------------------------------------------------------------
# Total Energy           = -59280.5155 eV
# Potential Energy       = -59280.5155 eV
# Ion Kinetic Energy     = 0.0000 eV
# ----------------------------------------------------------------
# NumOrb: Energy of system
# ----------------------------------------------------------------
# Charge                  = 1299.0797
# Band Structure Energy   = -11474.7884 eV
# ----------------------------------------------------------------
# El. Kinetic Energy      = 34169.8764 eV
# NL Energy               = -5004.6239 eV
# dEna                    = -1446.3624 eV
# dUscf                   = 142.9353 eV
# XC Energy               = -25778.3251 eV
# ENA                     = 14203.8958 eV
# Eions                   = -75567.9115 eV
# ----------------------------------------------------------------
# Electron kinetic energy = 34169.8764 eV
# Electrostatic energy    = -67672.0667 eV
# Exchange-corr. energy   = -25778.3251 eV
# ----------------------------------------------------------------
# Total potential energy  = -59280.5155 eV
# ----------------------------------------------------------------
Total energy
-59280.5154505 eV

i think it is correct, the total energy is of cource negtive.

but now, i have atk 13.8.1, i also compute the total energy for the same system,
the results is
| Total Energy Analysis                                                        |
|                                                                              |
+------------------------------------------------------------------------------+
| External-Field                     =    0.00000 eV                           |
| Exchange-Correlation               = -25927.35595 eV                         |
| Reservoir-Right                    =    0.81815 eV                           |
| Electrostatic                      =  640429.24008 eV                        |
| Reservoir-Left                     = -2857.35617 eV                          |
| Kinetic                            =  57743.49853 eV                         |
+------------------------------------------------------------------------------+
| Total energy                       =  669388.84464 eV                        |
+------------------------------------------------------------

I can see the total energy is positive.
i know there are some differences in the items which consists of total  energy in the 2008 and 13.8.1
but why the total energy is positive? i don not understand.


and the most important thing is i shall judge which spin configuration is more stable based on the total  energy.

the positive total energy is correct ?

[Anders Blom]

The positive result is not correct. I would guess the calculation has not converged, but without more information I can only guess. You have to always provide enough details for us to understand the issue. We have nothing but your numbers, no script, no output log, and then it's impossible to provide any guidance.