Liquid-Liquid Phase Transition in Elemental Carbon: A First-Principles Investigation

Wu, Christine J.; Glosli, James N.; Galli, Giulia; Ree, Francis H.

doi:10.1103/physrevlett.89.135701

Cited by 78 publications

(68 citation statements)

References 12 publications

(22 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Empirical potentials (22)(23)(24)(25) have also been used to investigate melting of carbon with different degrees of success. In general, empirical potentials lack predictive power over large density variations and, more specifically, important discrepancies between ab initio calculations and empirical potentials have been recently found, e.g., for the existence of a liquid͞liquid phase transition at low pressure (20,24,26).…”

mentioning

confidence: 99%

“…Empirical potentials (22-25) have also been used to investigate melting of carbon with different degrees of success. In general, empirical potentials lack predictive power over large density variations and, more specifically, important discrepancies between ab initio calculations and empirical potentials have been recently found, e.g., for the existence of a liquid͞liquid phase transition at low pressure (20,24,26).In this paper, we report on the properties of carbon in the pressure and temperature range of 15-2,000 GPa and 0-10,000 K, as obtained from first-principles calculations based on DFT. We have investigated solid͞liquid phase boundaries and analyzed structural and electronic transformations as pressure and temperature are increased.…”

mentioning

confidence: 99%

“…A number of experimental studies (16,17) and ab initio simulations (18)(19)(20) have focused on the phase boundaries close to the graphite-diamond-liquid triple point (Ϸ4,000 K and 15 GPa). Unlike other solids with the diamond structure (e.g., Si and Ge), at these pressures the melting line of carbon has a positive slope (19).…”

mentioning

confidence: 99%

See 2 more Smart Citations

Carbon under extreme conditions: Phase boundaries and electronic properties from first-principles theory

Correa

Bonev

Galli

2006

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

215

122

View full text Add to dashboard Cite

At high pressure and temperature, the phase diagram of elemental carbon is poorly known. We present predictions of diamond and BC8 melting lines and their phase boundary in the solid phase, as obtained from first-principles calculations. Maxima are found in both melting lines, with a triple point located at Ϸ850 GPa and Ϸ7,400 K. Our results show that hot, compressed diamond is a semiconductor that undergoes metalization upon melting. In contrast, in the stability range of BC8, an insulator to metal transition is likely to occur in the solid phase. Close to the diamond͞liquid and BC8͞liquid boundaries, molten carbon is a low-coordinated metal retaining some covalent character in its bonding up to extreme pressures. Our results provide constraints on the carbon equation of state, which is of critical importance for devising models of Neptune, Uranus, and white dwarf stars, as well as of extrasolar carbon-rich planets.phase transitions ͉ melting ͉ high pressure ͉ molecular dynamics ͉ metalization E lemental carbon has been known since prehistory, and diamond is thought to have been first mined in India Ͼ2,000 years ago, although recent archaeological discoveries point at the possible existence of utensils made of diamond in China as early as 4,000 before Christ (1). Therefore, the properties of diamond and its practical and technological applications have been extensively investigated for many centuries. In the last few decades, after the seminal work of Bundy and coworkers (2) in the 1950s and '60s, widespread attention has been devoted to studying diamond under pressure (3). For example, the properties of diamond and, in general, of carbon under extreme pressure and temperature conditions are needed to devise models of outer planet interiors (e.g., Neptune and Uranus) (4-6), white dwarfs (7, 8) and extrasolar carbon planets (9).Nevertheless, under extreme conditions the phase boundaries and melting properties of elemental carbon are poorly known, and its electronic properties are not well understood. Experimental data are scarce because of difficulties in reaching megabar (1 bar ϭ 100 kPa) pressures and thousands of Kelvin regimes in the laboratory. Theoretically, sophisticated and accurate models of chemical bonding transformations under pressure are needed to describe phase boundaries. In most cases, such models cannot be simply derived from fits to existing experimental data, and one needs to resort to first-principles calculations, which may be very demanding from a computational standpoint.It has long been known that diamond is the stable phase of carbon at pressures above several gigapascal (2). Total energy calculations (10, 11) based on Density Functional Theory (DFT) predict a transition to another fourfold coordinated phase with the BC8 symmetry ¶ at Ϸ1,100 GPa and 0 K, followed by a transition to a simple cubic phase at pressures Ͼ3,000 GPa. These transitions have not yet been investigated experimentally, because the maximum pressure reached so far in diamond anvil cell experiments on carbon is 140 GP...

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Carbon under extreme conditions: Phase boundaries and electronic properties from first-principles theory

Correa

Bonev

Galli

2006

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

215

122

View full text Add to dashboard Cite

show abstract

“…Thermodynamic databases helped develop fairly good bulk-thermodynamic free-energy functions that reproduce the low-temperature portion of the carbon phase diagram [4]. Because of the experimental difficulties, the theoretical (density functional) and numerical (MC and MD) methods of study of carbon phases gained popularity in the scientific community [5][6][7][8][9][10][11][12][13][14][15] graphite, diamond, and liquid carbon, although there is a number of high energy phases, e.g. bc8 and simple cubic, which were found to be metastable at low pressure and temperature [5] and stable at high pressure conditions [6].…”

Section: Carbon Phasesmentioning

confidence: 99%

“…Explanations of the maximum led to the introduction of two types of liquids: low-pressure graphite-like predominantly-sp 2 and high-pressure diamond-like predominantly-sp 3 [15]. Ree et al [9][10][11] conducted MD simulations and presented the isotherms of liquid carbon exhibiting a clear Van der Waals type dependence between the mostly sp 2 and sp 3 liquids. As a result, a liquid-liquid phase transition (LLPT) has been predicted.…”

Section: Carbon Phasesmentioning

confidence: 99%