TAILIEUCHUNG - Polyamorphism and two state model in liquid Geo2 under compression: Insight from visualization of molecular dynamics data
The distribution of OGey linkages in network structure is not uniform but tends to form clusters of OGey. The cluster of OGe2 will form low-density phase region, conversely the cluster of OGe3 will form high-density phase region. In other word, under compression, in the liquid GeO2 coexist two states: low-density and high-density. The size of phase regions significantly depends on compression. | Communications in Physics, Vol. 24, No. 3S1 (2014), pp. 95-98 DOI: POLYAMORPHISM AND TWO STATE MODEL IN LIQUID GEO2 UNDER COMPRESSION: INSIGHT FROM VISUALIZATION OF MOLECULAR DYNAMICS DATA NGUYEN VAN HONG, MAI THI LAN, NGUYEN THU NHAN Hanoi University of Science and Technology E-mail: Received 04 April 2014 Accepted for publication 24 August 2014 Abstract. The polyamorphism and two-state model based on the coordination number distribution in liquid GeO2 at 3200 K and in a wide pressure range are investigated by molecular dynamics simulation. Results show that the structure of liquid GeO2 mainly consists of GeOx coordination units (x = 4, 5, 6) and OGey linkages (y = 2, 3). The distribution of OGey linkages in network structure is not uniform but tends to form clusters of OGey . The cluster of OGe2 will form low-density phase region, conversely the cluster of OGe3 will form high-density phase region. In other word, under compression, in the liquid GeO2 coexist two states: low-density and high-density. The size of phase regions significantly depends on compression. Keywords: MD simulation, GeO. I. INTRODUCTION In recent years, a numerous studies focused on so-called polyamorphism and polyamorphic transitions in glass-forming liquids (such as GeO2 , SiO2 , TiO2 , H2 O, P. . . ). The polyamorphism and polyamorphic transitions were first recognized in the H2 O system. When compressed at 77 K, amorphous ice transforms from low-density to a high-density state at ± GPa [1-5]. Transitions between high density (HD) and low-density (LD) liquids have also been observed in the stable liquid regime for liquid phosphorus [6]. For liquid GeO2 , SiO2 and TiO2 it was found that when applying pressure, it transforms from tetrahedral to octahedral network structure. This corresponds to the transformation from LD phase to HD phase. In the 0-50 GPa pressure range, the structure of liquid GeO2 coexists both LD and HD .
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