[Pw_forum] Total energy of two isomeric compounds

[Romeda Azeen]

Dear Q.E Users
Greeting,
I'm also a new user of Q.E. I am studying the structural
properties of two isomeric compounds (TiCr, ZrCr). Accordingly, I make a
geometrical optimization for the these compounds i.e. determine the total
energy as a function of the lattice constant and then the data fitted to the
universal Murnaghan equation of state. 
I have a question about the obtained total
energy of these compounds? When, I have calculated the total energy of both compounds
to plot the total energy vs. volume/lattice constant, the obtained total energy
for TiCr is more negative compared to ZrCr?
Why the computed total energies are more
negative for TiCr? 
The obtained equilibrium lattice constants are
6.891 and 7.198 Å respectively for TiCr and ZrCr. The more negative energy can
be related to lattice constant? 
Can you help me?
 
Ti-Cr:
a(a.u.)            E(Ry)
12.3965    -929.59332904 
12.491     -929.61596146 
12.5855    -929.63374735 
12.68      -929.64697023 
12.7745    -929.65590118 
12.869     -929.66085069 
12.9635    -929.66198078 
13.0580    -929.65969906 
13.1525    -929.65417327 
13.247     -929.64537400 
13.3415    -929.63407783 
13.436     -929.62016514 
13.5305    -929.60373836 
13.625     -929.58513132 
13.719     -929.56461987 
--------------------------------------
Zr-Cr
12.6800     -894.4877      
12.7745     -894.52096     
12.869      -894.54919     
12.9635     -894.57259     
13.058      -894.59135     
13.1525     -894.60606     
13.247      -894.61653     
13.3415     -894.62354     
13.436      -894.62689     
13.5305     -894.62684     
13.625      -894.62369     
13.719      -894.61753     
13.814      -894.60833     
13.9085     -894.59663     
14.003      -894.58263     
14.0975     -894.56609     
14.192      -894.54736     
14.2865     -894.52646   
 
Sincerely,
Romeda Azeen
Bhavnagar University Bhavnagar
364002 Gujarat, India
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