GHEA Phase Models

                            Under construction

1. General rules 

1.1 Phase names

  1. The default choice, especially when the phase model is based on crystal structure, is the prototype name followed by _TY. This is especially useful when the same phase is stable in several systems.

  2. Chemical formula is generally used for phases modelled with reference to the stoichiometry, generally appearing in one or very few systems.

  3. Eexceptions to the mentioned rules are listed here below. 

    1. Strukturebericht symbol is used only for: A1 A2 A3 C14 C15 C36

    2. Greek letter used only for: SIGMA3 MU4 CHI

    3. Latin letter used only for: P3 R_PHASE

    4. FCC2 BCC2 (FCC4 BCC4) used for ordered phases based on A1 A2 respectively

  4. A number at the end of the phase name refers to the number of sublattices used in the model (e.g. SIGMA3, FCC2, FCC4, etc.)

  5. In all cases elements appearing in chemical formulas are ordered according to the Pettifor’s chemical scale reported here below  
    1  2  3  4  5  6  7  8  9  10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26  
    He Ne Ar Kr Xe Rn Fr Cs Rb K  Na Li Ra Ba Sr Ca Yb Eu Y  Sc Lu Tm Er Ho Dy Tb  

    27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52  
    Gd Sm Pm Nd Pr Ce La Lr No Md Fm Es Cf Bk Cm Am Pu Np U  Pa Th Ac Zr Hf Ti Nb  

    53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78  
    Ta V  Mo W  Cr Tc Re Mn Fe Os Ru Co Ir Rh Ni Pt Pd Au Ag Cu Mg Hg Cd Zn Be Tl  

    79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103  
    In Al Ga Pb Sn Ge Si B  Bi Sb As P  Po Te Se S  C  At I  Br Cl N   O   F   H

1.2 Sublattices

  1. Integer numbers are preferentially used to express stoichiometric ratios between sublattices

  2. For phase models based on crystal structure, sublattices are ordered according to the decreasing coordination of the corresponding crystallographic sites. This often corresponds to the decreasing atomic radius of the occupying elements and to the position of the elements in the Pettifor’s scale.

  3. For phase models based on stoichiometry, sublattices are ordered according to the order of the occupying elements in the Pettifor’s scale formula (i.e. the order of the elements in the chemical formula).


 


Table Phase Models

 

Phase type

Phase Name

(other names)

Selected Stable Compositions

Pearson symbol

Prototype

Space group

Sublattice model (Wyckoff,Coordination:constituents)

TDB format

Remarks

FCC

A1  
(fcc, γ)

(Al)  
(Co)  
(Ni)

cF4

Cu

Fm-3m

Model: (4a,12:M)1 (4b,6:X,Va)1  
PHASE A1 %M 2 1 1 !  
CONST A1 :AL%,CO%,CR,FE,HF,MO,NI%,RE,SI,TA,TI,W,Y : B,C,VA% : !

Magnetic contribution  
Second SL for octahedral interstitial sites  
Disordered contribution to the ordered FCC2 phase

FCC  
ORD/DIS

FCC2  
(L12, γ‘)

Ni3Al

cP4

AuCu3

Pm-3m

Model: (3c,12:M)0.75 (1a,12:M)0.25 (1b+3d,6:X,Va)1  
PHASE FCC2 %Q 3 .75 .25 1 !  
CONST FCC2 :AL,CO,CR,FE,HF,MO,NI%,RE,SI,TA,TI,W,Y   
:AL%,CO,CR,FE,HF,MO,NI,RE,SI,TA,TI,W,Y : B,C,VA% : !

Magnetic contribution  
Ordered phase with a disordered contribution from A1

FCC  
CARBIDE

MC  
(B1, MC carbide)

TaC  
WC

cF8

NaCl

Fm-3m

Model: (4a,12:M)1 (4b,6:C)1   
PHASE MC %M 2 1 1 !  
CONST MC :CO,CR,MO,NI,TA%,W% : C%,VA : !

Magnetic contribution  
This is the same as A1 with second SL almost filled by C

BCC

A2  
(bcc, α)

(Cr)  
(Mo)  
(Ta)  
(W)

cI2

W

Im-3m

Model: (2a,8+6:M)1 (3c,6:X,Va)3  
PHASE A2 %N 2 1 3 !  
CONST A2 :AL,CO,CR%,FE,HF,MO%,NI,RE,SI,TA%,TI%,W%,Y,VA : B,C,VA% : !

Magnetic contribution  
Second SL for octahedral interstitial sites  
Disordered contribution to the ordered BCC2 phase

BCC  
ORD/DIS

BCC2  
(B2, β)

NiAl

cP2

NiAl


 

Pm-3m

Model: (1a,8+6:M)0.5 (1b,8+6:M)0.5 (3c,6:X,Va)3   
PHASE BCC2 %AN 3 0.5 0.5 3 !  
CONST BCC2 : AL,CO,CR%,FE,HF,MO,NI,RE,SI,TA%,TI,W%,Y,VA   
: AL,CO,CR,FE,HF,MO,NI,RE,SI,TA,TI,W,Y,VA : B,C,VA : !

Magnetic contribution  
Ordered phase with a disordered contribution from A2

HCP

A3  
(hcp, cph)


 

(Co)  
(Re)

hP2

Mg


 

P63/ mmc

Model: (2c,12:M)1 (½ 2d,6:X,Va)0.5  
PHASE A3 %M 2 1 .5 !  
CONST A3 :AL,CO%,CR,FE,HF%,MO,NI,RE%,SI,TA,TI%,W,Y : B,C,VA% : !

Magnetic contribution  
Second SL for octahedral interstitial sites

HCP  
ORD

D0_19  
(D019)

WCo3  
Ta(Co,Ni)3  
AlTi3

hP8

Mg3Cd

or

Ni3Sn

P63/mmc

Model (3c,12:M)0.75 (1a,12:M)0.25 (4b,6:X,Va)1  
PHASE D0_19 % 3 1 3 2 !  
CONST D0_19 : AL,CO,CR,MO,NI,TA%,TI,W%,Y% : AL,CO%,NI%,TA,TI,W : C,VA% : !

Ordered form of A3 (2x2x1 superstructure) but ordering is not modelled

HCP  
CARBIDE

M2C  
(C6, M2C carbide)

Ta2C  
W2C

hP3

CdI2


 

P-3m1

164

Model: (2c,12:M)1 (½ 2d,6:X,Va)0.5  
PHASE M2C %M 2 1 .5 !  
CONST M2C :CO,CR,NI,TA%,W% : C%,VA : !

Magnetic contribution  
This is the same as A3 with second SL almost filled by C  
Modelled as 1:0.5 instead of 2:1 to be consistent with A3.


 

ALPHA_B

B


 


 


 

Model: (X)1   
PHASE ALPHA_B % 1 1.0 !  
CONST ALPHA_B :B : !

Solubility of metals in this phase is neglected


 

BETA_B

B

hR36

betaB

R-3m

Model: (X)1   
PHASE BETA_B % 1 1.0 !  
CONST BETA_B :B : !

Solubility of metals in this phase is neglected


 

DIAMOND

C

cF8

C-diam

Fd-3m

Model: (X)1   
PHASE DIAMOND % 1 1.0 !  
CONST DIAMOND :C,SI : !

Solubility of metals in this phase is neglected


 

GRAPHITE

C

hP4

C-graph

P63/ mmc

Model: (X)1   
PHASE GRAPHITE % 1 1.0 !  
CONST GRAPHITE :B,C : !

Solubility of metals in this phase is neglected

BCC  
ORD

CSCL_TY

ReAl

cP2

CsCl

Pm-3m

Model: (Re)1 (Al)1  
PHASE CSCL_TY % 2 1 1 !  
CONST CSCL_TY : RE : AL : !

This is the same crystal structure of BCC2 but it is not considered an ordered form of A2

FCC  
ORD

L1_0  
(L10)

TiAl

tP4

AuCu

P4/mmm

Model: (1a+1c,12:M)1 (2e,12:M)1 (1b+1d+2f,6:X,Va)2  
PHASE L1_0 % 3 1 1 2 !  
CONST L1_0 :AL,TI% : AL%,TI : C,VA% : !

Ordered form of A1 but ordering is not modelled  
Last sublattice is for octahedral interstitial sites

LAVES

C14

TaCo2  
TaCr2

hP12

MgZn2

P63/mmc

Model: (4f,16:LM)1 (2a+6h,12:SM)2  
PHASE C14 %M 2 1 2 !  
CONST C14 :AL,CO,CR,FE,HF,MO%,NI,TA%,TI%,W,Y   
:AL,CO%,CR%,FE,HF,MO,NI,RE, TA,TI, W : ! 


 

LAVES

C15

TaCo2,  
TaCr2

cF24

MgCu2


 

Fd-3m

Model: (8a,16:LM)1 (16d,12:SM)2  
PHASE C15 %M 2 1 2 !  
CONST C15 : AL,CO,CR,FE,HF,NI,TA%,TI,W,Y%   
: AL,CO%,CR%,FE,HF,NI%,TA,TI,Y : ! 


 

LAVES

C36

TaCo2

hP24

MgNi2


 

P63/mmc

Model: (4e+4fI,16:LM)1 (4fII+6g+6h,12:SM)2  
PHASE C36 %M 2 1 2 !  
CONST C36 : CO,CR,NI,TA%,TI,W : AL,CO%,CR,NI,TA,TI : !


 

TCP

SIGMA3

σ(Co,Cr)

tP30

CrFe


 

P42/mnm

Model: (4f,15:LM)2 (8iI+8j,14:LM)8 (2a+8iII,12:SM)5  
PHASE SIGMA3 % 3 2 8 5 !  
CONST SIGMA3 :AL,CO,CR%,FE,MO,NI,RE,TA,W% : AL,CO,CR%,FE,MO,NI,RE,TA,W%   
:AL,CO%,CR,FE,MO,NI%,RE,TA,W : ! 

Stability based on VEC more than atomic dimensions

TCP

MU4

μ(Ta,Co)  
μ(W,Co),  
μ(Ta,Ni)

hR36

W6Fe7


 

R-3m

Model (6c'+6c”,16-15:LM)4 (6c”',14:LM)2 (3a,12:SM)1 (18h,12:SM)6  
PHASE MU4 % 4 4 2 1 6 !  
CONST MU4 : AL%,CO,MO%,TA%,W% : AL%,CO,CR,FE,MO,NI,TA%,W%   
: AL,CO%,CR%,FE%,MO,NI%,TA,W : AL,CO%,CR%,FE%,MO,NI%,TA,W : !

Stability based on VEC more than atomic dimensions

      ...in progress 

 

 

 

 

Last update 26 May 2023