THE MASS-RADIUS RELATION HAS PLAYED A CENTRAL ROLE IN UNDERSTANDING THE COMPOSITIONS OF THE EXTRASOLAR PLANETS FROM ASTROPHYSICAL MEASUREMENTS WHERE IT HAS BEEN ASSUMED THAT GAS ICE ROCK AND METAL DO NOT REACT WITH EACH OTHER SIGNIFICANTLY AND THAT THEY THEREFORE FORM SEPARATE LAYERS IN THE INTERIORS OF THE EXOPLANETS. SPECIFICALLY SOME LARGE EXOPLANETS WITH SLIGHTLY LOWER DENSITY THAN SUPER-EARTH HAVE BEEN MODELED AS WATER WORLDS WHERE THE ROCKY MANTLE IS OVERLAIN BY A FEW HUNDREDS TO THOUSANDS OF KILOMETERS THICKNESS OF ICE. FOR ICY AND GAS GIANT EXOPLANETS A MECHANICAL MIXTURE OF ICE AND ROCK HAS BEEN USED TO MODEL THE CORE. ALTHOUGH THE EQUATIONS OF STATE OF ROCK METAL ICE AND GAS HAVE BEEN EXTENSIVELY STUDIED INDIVIDUALLY THEIR MUTUAL INTERACTIONS AT PRESSURETEMPERATURE CONDITIONS OF THE INTERIORS OF LARGE EXOPLANETS REPRESENT A NEW AND COMPLETELY UNEXPLORED PLANETARY PARADIGM. OUR RECENT EXPERIMENTS HAVE SHOWN THAT PRESSURE ALLOWS MORE WATER TO BE INCORPORATED INTO THE CRYSTAL STRUCTURE OF SILICA. EXTRAPOLATION OF THIS TREND PREDICTS THAT ICE AND SILICA MAY EVEN FORM SOLID SOLUTIONS ABOVE 100 GPA. BECAUSE OF THEIR HITHERTO UNKNOWN THERMOELASTIC PROPERTIES THE EXISTENCE OF STABLE ROCK-ICE ALLOYS WOULD HAVE A PROFOUND IMPACT ON THE INTERPRETATION OF EXOPLANETARY MASS-RADIUS RELATIONS BASED ON THE CONVENTIONAL NOTION OF DISTINCT GAS ICE ROCK AND METAL COMPONENTS. WE WILL UNDERTAKE A SYSTEMATIC STUDY OF POTENTIALLY NEW CLASSES OF MATERIALS FORMED FROM ICE-ROCK REACTIONS IN THE DEEP INTERIORS OF EXOPLANETS BY COMBINING EXPERIMENTS AND THEORETICAL SIMULATIONS. THE OVERARCHING GOAL IS TO IDENTIFY THE PRESSURE-TEMPERATURE CONDITIONS WHERE THE TRADITIONAL ROCK AND ICE BARRIER BREAKS DOWN AND A NEW CLASS OF MATERIALS FORMS IN THE SI-O-H SYSTEM AND ULTIMATELY PROVIDE UPDATED MASS-RADIUS RELATIONS FOR EXOPLANET RESEARCH. DENSITY FUNCTIONAL THEORY WILL BE USED TO DEVELOP A PLAUSIBLE RANGE OF CRYSTALLINE MODELS OF SILICA-ICE SOLID SOLUTION PHASES AND PREDICT THEIR EQUATIONS OF STATE. THE PRESSURE-TEMPERATURE STABILITY FIELDS OF EACH CANDIDATE PHASE ASSESSED BY COMPARING ITS FREE ENERGY TO THAT OF A CORRESPONDING SILICA+ICE MIXTURE. THE MOST FAVORABLE CANDIDATE PHASES IDENTIFIED IN THIS INITIAL STEP WILL THEN INFORM HIGH PRESSURE EXPERIMENTS. IN EXPERIMENTS WE WILL SYSTEMATICALLY EXPLORE THE REACTIONS BETWEEN SILICA AND ICE AT IN SITU HIGH PRESSURE AND HIGH TEMPERATURE IN THE LASER-HEATED DIAMOND-ANVIL CELL. RAMAN AND INFRARED SPECTROSCOPY WILL BE CONDUCTED FOR THE SAMPLES AT ASU IN ORDER TO MAP THE STABILITY FIELDS OF NEW PHASES IN THE SI-O-H SYSTEM. IN SITU SYNCHROTRON X-RAY DIFFRACTION AT HIGH TEMPERATURES AND PRESSURES ALLOWS US TO DIRECTLY OBTAIN STRUCTURAL INFORMATION AND THE EQUATIONS OF STATE OF THE NEW PHASES. THE COMBINED EXPERIMENTAL AND COMPUTATIONAL RESULTS WILL THEN BE USED TO CONSTRUCT NEW MASS-RADIUS RELATIONS FOR THE EXOPLANET DATA ANALYSIS. THE PROPOSED RESEARCH WILL COMBINE FOR THE FIRST TIME TARGETED LABORATORY AND FIRST PRINCIPLES SIMULATIONS EFFORTS TO EXPLORE NEW CHEMISTRY IN THE SI-O-H SYSTEM WHOSE COMPONENTS HAVE BEEN TRADITIONALLY CONSIDERED INCOMPATIBLE WITH ONE ANOTHER. AS SUGGESTED IN OUR PRELIMINARY STUDY IF THE BARRIER BETWEEN ROCK AND ICE BREAKS DOWN IN THE INTERIORS OF LARGE EXOPLANETS IT WILL HAVE PROFOUND IMPLICATIONS FOR THE INTERPRETATIONS OF EXOPLANETARY COMPOSITIONS FROM THE MASS-RADIUS RELATION. THE EXPECTED MAIN OUTCOME OF THIS RESEARCH PROJECT IS IMPROVED MASS-RADIUS RELATIONS WHICH ARE EXPECTED TO AFFECT INTERPRETATION OF A WIDE RANGE OF EXOPLANETS INCLUDING GAS GIANTS ICY GIANTS MINI-NEPTUNES AND WATER WORLD EXOPLANETS. THEREFORE OUR PROPOSED RESEARCH WILL HAVE IMMEDIATE IMPACTS FOR THE ONGOING AND NEAR FUTURE OBSERVATIONS USING GROUND-BASED TELESCOPES AND SPACE TELESCOPES (SUCH AS CHEOPS TESS AND GAIA) WHICH WILL DRAMATICALLY IMPROVE THE PRECISION OF MEASURED RADII AND MASSES OF THE EXOPLANETS.