Physica B 595 (2020) 412350 Available online 8 July 2020 0921-4526/© 2020 Elsevier B.V. All rights reserved. A new perspective to thermodynamical designing of high entropy bulk metallic glasses (HE-BMGs) Anurag Bajpai a , Jatin Bhatt b , Krishanu Biswas a, * , Nilesh P. Gurao a a Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur, Uttar Pradesh, India b Department of Metallurgical and Materials Engineering, Visvesvaraya National Institute of Technology, Nagpur, Maharashtra, India A R T I C L E INFO Keywords: High entropy bulk metallic glasses Cluster packing Mismatch entropy Electronic shell number Fermi radius ABSTRACT The present investigation involves an attempt to incorporate key thermodynamical and topological aspects of glass formation specifically the enthalpy of chemical mixing (ΔH mix ), configurational entropy (ΔS config ) and entropy due atomic size mismatch (ΔS σ ) into a single parameter using the P HSS model to understand their role in designing new HE-BMG compositions. The model has been employed with 69 elements for quinary equiatomic alloys to investigate the possibilities of the alloys to form HE-BMGs. The application of the hard-sphere atomic radius in the evaluation of topological parameters through the P HSS model appears to be insufficient in designing new HE-BMG alloy systems due to the limitations of some of the associated assumptions. Most importantly, the effect of the alteration of the local electronic environment of atoms on their atomic radii in multi-component alloys has been incorporated into the model to further establish the defining role of topology in glass forma- tion. The results revealed that the number of quinary equiatomic alloys forming HE-BMG systems is 368,275 (3.75% of 9,818,072 ( 69 C 5 ) total combinations). The modification in atomic radii has been found to pinpoint more precisely the HE-BMG alloy systems when compared to the hard-sphere model for atomic radii of pure elements. In a nutshell, this kind of statistical modelling approach can lead to the development of unprecedented determination of new HE-BMG compositions. 1. Introduction High entropy alloys (HEAs) [1–8], as well as bulk metallic glasses (BMGs) [9,10], have attracted considerable research attention in recent times. HEAs are defined as multi-component alloys containing at least five elements in equiatomic or near equiatomic (5–35 at. %) concen- trations. An intense interest in HEAs has developed due to their excep- tional mechanical properties, such as large elastic limits, high strength as well as hardness, good corrosion and wear resistance. On the other hand, bulk metallic glasses (BMGs) are metallic alloys whose atomic-scale structure is inherently disordered in nature. They lack translational periodicity and are devoid of defects such as dislocations and grain boundaries which imparts them with unique physical, me- chanical and chemical properties, such as high strength, toughness, hardness, corrosion, and wear resistance [9–14]. On account of these outstanding properties, they are used in a wide range of applications including striking faceplate in golf clubs, watch parts, casing in cellular phones, connecting parts for optical fibres, optical mirrors, high-density information-storage materials, micro-electromechanical systems (MEMS), high sensitivity small pressure sensors, slat truck cover for aircrafts, and jewellery [15,16]. Recently, the definition of HEAs has been extended to include BMGs giving birth to a new class of High en- tropy bulk metallic glasses (HE-BMGs). Such alloys exhibit both the features of HEAs with respect to their composition and those of bulk metallic glasses due absence of long-range structure order [17]. These alloy systems have been found to exhibit better mechanical properties when compared to their parent bulk metallic glasses generating further interest in their research and development [18–21]. However, the HE-BMGs systems discovered till date are less in number and thus, the design of appropriate equiatomic multi-component alloy compositions is the key to the development of novel HE-BMGs. Hence, the development of a novel thermodynamics based strategy has been warranted for a long time. An alloy design approach must involve answering a critical question regarding the ability to envisage the nature of phases (solid solution, amorphous or intermetallic) which may form for a given composition for a set of constituent elements. Regarding designing metallic glass sys- tems, several qualitative and quantitative design methodologies have * Corresponding author. E-mail address: kbiswas@iitk.ac.in (K. Biswas). Contents lists available at ScienceDirect Physica B: Physics of Condensed Matter journal homepage: http://www.elsevier.com/locate/physb https://doi.org/10.1016/j.physb.2020.412350 Received 2 May 2020; Accepted 23 June 2020