THE p-T PHASE DIAGRAM OF OXYGEN DETERMINED BY RAMAN SCATTERING

HAL Id: jpa-00224335

https://hal.archives-ouvertes.fr/jpa-00224335

Submitted on 1 Jan 1984

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

THE p-T PHASE DIAGRAM OF OXYGEN DETERMINED BY RAMAN SCATTERING

H. Hochheimer, H. Jodl, F. Bolduan

To cite this version:

H. Hochheimer, H. Jodl, F. Bolduan. THE p-T PHASE DIAGRAM OF OXYGEN DETERMINED BY RAMAN SCATTERING. Journal de Physique Colloques, 1984, 45 (C8), pp.C8-195-C8-198.

�10.1051/jphyscol:1984835�. �jpa-00224335�

THE p-T PHASE DIAGRAM OF OXYGEN DETERMINED BY RAMAN SCATTERING

H.D, Hochheimer, H.J. Jodl* and F. Bolduan Max-planck-Inetitut far FestWrpevfovsahung, 7000 Stuttgart BO, F.R.C.

Resume - Le diagramme p-T de phase de l'oxygene liquide et solide a &t£ gtabli dans 1' intervalle de temperature 6 - 300 K et pour des pressions allant jusgu'S Id GPa an moyeri de l'effet Raman.

Abstract - The p-T phase diagram of liquid and solid oxygen in the temperature range from 6 - 300 K and pressures up to 14 GPa has been determined by Raman scattering.

Solid molecular oxygen has generated considerable interest, due to the fact that the two unpaired electrons in the outer shell of 0-, from a triplet spin state. Therefore in solid oxygen additional magnetic interactions have to be considered, which lead to a great wealth of crystalline phases. We have performed a high pressure

Raman study to determine the phase diagram of fluid and solid oxygen between 6 and 300 K at pressures up to 14 GPa. Experimental details are given in ref. 1

The structure of a - 02 {C2/m) ,oc* - or 'orange' 07 (Fmmrn) , JJ-0- {R3m}, and y-O, (Pm3m) are known, whereas the structure of a-0- and £-0~

in Fig. 1 and Fig. 4 are unknown.

Fig. 1 The p-T phase diagram of molecular oxygen prior to our work.

The phase boundaries in the low temperature region are taken from ref. 2 and i : »fO , B : data from ref. 4; o: ref. 5; the dashed line is taken from ref. 6.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984835

C8-196 JOURNAL DE PHYSIQUE

The Raman spectra of the external and internal modes allow the

determination of the liquid -y, y-6-, 6-a- and 13-&phase lines unam- biguously. Unfortunately the Raman spectra of a-,

z-,

show the same general features (Fig. 2) and do therefore not allow an unambiguous determination of the phase transitions.

RAMAN FREQUENCY SHIFT Lcm-11

Fig. 2

Raman spectra of solid oxygen in the low energy region

Therefore discontinuities in the slopes of the frequency versus pressure curves of the librations and vibrations (Fig. 3) have been used to determine the a - T and a-a@- phase lines.

The a ' - €-phase line was determined using the assumption that the

sudden drop in the vibration frequency versus pressure curves of constant temperatures indicates the phase transition pressure.

I- LL

quencies of solid oxygen at 10 K

Lo

&

Z W 3 200--

0 W . LI LL

150-

The results of our measurements are comprised in Fig. 4

- ,*'.

- ^Libration

I /

- ,',,'

/

: '

- ,-"

.'

, /.'

- i _,, ,,

PRESSURE [GPa]

J'

J"

50 -

r , ,

^,

^{, -}

0 2 4 6

PRESSURE IGPal

Fig. 4 The p-T phase diagram of oxygen determined from our Raman experiments

C8-198 JOURNAL DE PHYSIQUE

Recent powder X-ray diffraction measurements of Olinger et al.

'

298 K up to 13 GPa indicate the existence of two other high pressure phases and give the hint that the structure of E-O2 may be an ortho- rhombic disortion of a-02.,However more efforts

both theoretical and experimental are necessary to achieve a more complete understandig of solid oxygen.

REFERENCES

1. HOCHHEIMER H.D., JODL H.J., HENKEL W., BOLDUAN F., Chem. Phys.

Letters

106

2. STEWART J.W., J. Phys. Chem. Solids

12

3. MEIER R.J., SCHINKEL C.J., DE VISSER A., J. Phys. C

15

4. NICOL M., HIRSCH K.R., HOLZAPFEL W.B., Chem. Phys. Letters

68

(1979) 49.

5. YAGI T., HIRSCH K.H., HOLZAPFEL W.B., J. Phys. Chem.

87

6. YEN J., NICOL M., J. Phys. Chem. 87 (1983) 4616.

7. OLINGER B., MILLS R.L., ROOF I r . ~ x . , to be published in J. Chem.

Phys.

*permanent address: FB Physik, Universitat Kaiserslautern, Erwin-Schr6dinger-StraBe

6750 Kaiserslautern, FRG.