No energy minimum lattice in some Cd and Hg alloys

Posted on : June 30, 2018 (Sat) 16:40:54

by Taewon Jin

Dear professors

I tried to calculate the Cd and Hg alloys with various volume to find optimized volume

Here is the input file I used:

c---------------------FeCo----------------------------------
go ./data/mag/FFFF-bcc-28-80-25-5.6
c------------------------------------------------------------
c brvtyp a c/a b/a alpha beta gamma
bcc 5.6, , , , , ,
c------------------------------------------------------------
c edelt ewidth reltyp sdftyp magtyp record
0.001 1.0 sra gga91 mag init
c------------------------------------------------------------
c outtyp bzqlty maxitr pmix
update 11 500 0.01
c------------------------------------------------------------
c ntyp
1
c------------------------------------------------------------
c type ncmp rmt field mxl anclr conc
FeCo 2 0 0.0 2
28 75
80 25
c------------------------------------------------------------
c natm
1
c------------------------------------------------------------
c atmicx(in the unit of a) atmtyp
0a 0b 0c FeCo
c------ The following types of inputs and their combination
c are also allowed.
c------ In those cases a, b, b mean primitive unit vectors
c and x, y, z mean shortest unit cell vectors along
c x, y, and z axses.
c 1/2 1/2 1/2 Fe
c 0a 0b 0c Fe
c 0x 0y 0z Fe
c 1/2a 1/2b 1/2c Fe
c------------------------------------------------------------


and here is the total energy output of various volume.

some alloys shows that there is no minimum data with large volume
(5.6 ~ 7.0 are lattice parameter of Ni0.75Hg0.25)

as volume increase, total energy decrease linearly and it seems there is no minimum data.

bcc-28-75-80-25-5.6: total energy= -12073.3683839
bcc-28-75-80-25-5.7: total energy= -12073.6325132
bcc-28-75-80-25-5.8: total energy= -12073.8746239
bcc-28-75-80-25-5.9: total energy= -12074.1209851
bcc-28-75-80-25-6.0: total energy= -12074.3473338
bcc-28-75-80-25-6.1: total energy= -12074.5518777
bcc-28-75-80-25-6.2: total energy= -12074.7496060
bcc-28-75-80-25-6.3: total energy= -12074.9459123
bcc-28-75-80-25-6.4: total energy= -12075.1374990
bcc-28-75-80-25-6.5: total energy= -12075.3348339
bcc-28-75-80-25-6.6: total energy= -12075.5210637
bcc-28-75-80-25-6.7: total energy= -12075.7155416
bcc-28-75-80-25-6.8: total energy= -12075.8961307
bcc-28-75-80-25-6.9: total energy= -12076.0913719
bcc-28-75-80-25-7.0: total energy= -12076.2649733

Some Cd alloy shows similar result.

Some Cd & Hg alloy originally not prefer alloying? or

Do I need to fix parameter to find energy minimum?